MIDWINTER ENCHANTMENT IN THE BEAR CREEK NATURE PRESERVE
AT CASITAS DE GILA GUESTHOUSES IN SOUTHWEST NEW MEXICO
January 22, 2017 at Casitas de Gila on Bear Creek, looking north to the Gila Wilderness covered in deep snow
SOUTHWEST NEW MEXICO: A NATURE LOVER’S PARADISE WITH FOUR GENTLE SEASONS
The High Chihuahuan Desert of Southwest New Mexico is a landscape of exceptional beauty, diversity, and distinct seasonal climatic change due to a rugged topography ranging from 4,000 to 11,000 feet. For the city or urban dweller longing to reconnect with millions of acres of pristine and untrammeled Nature, the lowland deserts, soaring mountains, and numerous rivers and creeks of the vast Gila Wilderness, Gila National Forest and other public lands in Southwest New Mexico offer an unlimited array of outdoor opportunities that can be enjoyed every season of the year … including Winter!
Situated on 265 private acres on Bear Creek, near to and directly overlooking the Gila Wilderness and National Forest, Casitas de Gila Guesthouses has since 1999 specialized in providing its guests with the best directions and information regarding access to, knowledge of, and pursuit of the various outdoor activities possible on these public lands. In addition, Casitas de Gila is most fortunate in having been able to develop within its own property the Bear Creek Nature Preserve, a unique landscape that offers Casita guests an exceptional connection and access with Nature right out the door of their Casita to over six miles of trails along Bear Creek and the adjacent mountains.
In Winter, Cottonwoods cast long shadows across trails along Bear Creek
THE WINTER OF 2016-17: AN EXCEPTIONAL DISPLAY OF NATURE’S SURPRISE, MAGIC,
AND CHANGE WITHIN THE BEAR CREEK NATURE PRESERVE
In most years, Winter at the Casitas and the Bear Creek Nature Preserve is a rather laid-back season, a time for quiet personal reflection on the year gone by. It’s a time for leisurely walks on sun-dappled paths beneath towering groves of the leafless Cottonwood and Willow that line the tranquil, faintly gurgling waters of Bear Creek. Or a time for an exhilarating climb up the more challenging trail just across Bear Creek leading to a magnificent 360° panorama at the top of Paradise Overlook Mountain. Or, if the spirit is feeling a little more restless and adventurous, one might head out to the nearby spectacular Catwalk Recreation Area, the intriguing Gila Cliff Dwellings National Monument, or one of the many beckoning nearby trails in the Gila Wilderness and National Forest. Later, as the afternoon shadows lengthen and the temperature begins to fall, it is time to return to the comforts of one’s own warm Casita to end the day with a relaxing meal, followed by a good book in front of a crackling fire in the kiva fireplace, a serious game of Scrabble or Monopoly, or maybe even putting together a 1000-piece puzzle! Ah yes, that has been the Winter experience at the Casitas for most years. But so far, this Winter has certainly not been like most!
A WINTER OF SURPRISING WETNESS BEGINS …
Jet Stream pattern responsible for White Christmas at Casitas, Dec. 25, 2016 (source: squall.sfsu.edu/crws.html)
Jet Stream map showing cutoff loop bringing moisture from Baja California to Casitas on Dec. 22, 2016. (Source: CA Regional Weather Server, Dept of Earth & Climate Sciences, San Francisco State Univ, squall.sfsu.edu/crws.html)
Weather wise, early Fall at the Casitas in 2016 was essentially normal, a little drier perhaps and somewhat warmer, but typical great weather for outdoor pursuits. During the first three weeks of December this pattern continued for the greater part, but with interspersed short periods of clouds, minor precipitation, and colder than average weather in response to repeated events in which the Arctic jet stream would loop south from Canada down the US West Coast and then into Southwest New Mexico.
Then, on December 22, the first of what would become a month-long series of abnormal precipitation events began, when a persistent, cut-off segment of one of these Arctic Jet Stream loops began pumping a cell of Low Pressure moisture from Baja California across the Southwest into New Mexico, bringing the Casitas over an inch of rain. At the Casitas, most of this rain was quickly absorbed by the very dry ground. Bear Creek, however, rose several inches in response, making access to the trails on the other side of the creek a little more difficult, but still doable for most of the guests who were now coming in for the holidays. Following a brief day of clearing, on Christmas Eve the clouds came in once more as a new Arctic Jet Stream loop of cold air pushed down from the North to collide with a still active Southern Jet Stream segment that was pumping moist Low Pressure air in from Baja California.
Christmas morning 2016 at Casitas de Gila, looking north to the Gila Wilderness (hidden in clouds)
The snow began falling after midnight and by morning the Casitas awoke to a big surprise: a magnificent White Christmas with three inches of snow coating everything in sight. By early afternoon, temperatures had warmed considerably as the Arctic loop of cold air dissipated, melting all of the snow except in the higher elevations in the Gila Wilderness mountains to the north. Over the next few days a persistent plume of Jet Stream coming up from Baja California continued to bring warm, cloudy, moist unsettled weather in over Southwest New Mexico, culminating with a major storm on December 31, to finish out the month of December with over two inches of rain at the Casitas. Throughout this time water levels in Bear Creek continued to rise as the rain and warm weather melted the snow in the higher mountains, rendering trail stream crossings in the Bear Creek Nature Preserve impossible. Outdoor pursuits elsewhere in the surrounding area were likewise severely curtailed as the same storms caused numerous problems: highways, roads and destinations were closed by snow or washed out, including the Gila Cliff Dwellings and the Catwalk, as well as many of the trails of the Gila Wilderness and National Forest. Two groups of hikers in the Gila Wilderness had to be helicoptered to safety on Christmas Day when land based rescue teams could not reach them because of high water on tributaries of the Gila River.
Jet Stream loop responsible for bringing 1-1/2 inches of rain to the Casitas January 14-16, 2017 (source: squall.sfsu.edu/crws.html)
Jet Stream pattern responsible for bringing persistent clouds and moisture to Casitas from Pacific and Baja California for first week and a half of January 2017 (source: squall.sfsu.edu/crws.html)
During the first week and a half of January, another strong Southern Jet Stream flow continued to bring in clouds, moist air, and various amounts of rain from the Pacific and Baja California to Southwest New Mexico, keeping Bear Creek running high, fast, and uncrossable. Not to be deterred, however, intrepid Casita guests ventured out on most days to give the various trails on the Casita side of the Creek a good workout or hiking Gila Wilderness trails that still remained open. On the bad days, they stayed inside their cosy Casita reading by the kiva fire, besting their partner at Scrabble, completing that puzzle, keeping up with the outside world on the Internet, or simply resting up for that all-to-soon return to the outside world. Elsewhere in the area, the Catwalk, Cliff Dwellings, and many Gila Wilderness and National Forest trails remained closed.
Then … surprise again! Just when one thought the rain was over, another Arctic loop came down from the north for another three days, dropping another inch and a half of rain from January 14-16 before gradually moderating into three days of patchy clouds, wind, and cold, but without rain. An improvement! But not for long, as, totally unsurprising at this point, on the 20th yet another major Arctic loop dropped down from the north bringing more than an inch of rain over the next four days for a total monthly rainfall on January 24, 2017, of 2.68 inches!
Is the Midwinter Deluge of 2017 over? Well, as of January 24th, the five-day Jet Stream forecast looks promising, and the ten-day Weather Underground forecast reads clear and sunny with rising temperatures! We shall see …
SOME MAGIC AND CHANGE EXPERIENCED WITHIN THE BEAR CREEK NATURE PRESERVE DURING THE DELUGE OF 2016-17
Bear Creek out of its channel and flowing across the adjacent floodplain, making crossing the creek impossible
Put in historical perspective, the Midwinter Deluge of 2016-17 was a truly-unique Winter weather event during the 18 years of operation of Casitas de Gila Guesthouses. Never during that period has this much rain (4.5 inches in 5 weeks) fallen in such a short time at this time of year, turning seasonally placid and faintly gurgling Bear Creek into an raging, growling Bear RIVER for over a month! The closest similar Winter Season event was the Great Flood of February 12, 2005, when a slow-moving warm front coming up from Mexico dropped 2.5 inches of rain over a three-day period over the entire Bear Creek drainage and also melted most of that Winter’s snow pack in the Pinos Altos Mountains and Silver City Range in the headwaters of Bear Creek. The combined runoff from that storm resulted a two-week flood at the Casitas that crested at 8 feet above normal level, and relocated the channel from the east side to the west side of the floodplain in front of the Casitas.
During most of the time period covered in this blog, half of the floodplain trails and the trail up Paradise Overlook Mountain on the east side of Bear Creek remained unreachable because of high water. All of the numerous trails along the west side of the floodplain below the Casitas, however, remained accessible, offering guests unique opportunities to experience up close and personal the magic, the many changes taking place, and insight into cause and effects of Nature’s unleashed power that were unfolding below their Casita on a daily basis.
Entering the grove of Gray Oaks by Bear Creek, the trail passes through a fantasy world of white lace on gnarled branches!
Along the trail heading down to Bear Creek and the cliffs beyond
No matter what the season, unexpected moments of Nature’s Magic are frequent at the Casitas for those who seek them, whether just sitting in front of the Casita on the edge of the Canyon gazing out at Bear Creek below and the mountainous Gila Wilderness beyond, or while answering the call of the ever-beckoning trails. In Spring, it might be the sudden encounter of a profusion of rare wild flowers blooming along one of the Casita trails. In Summer, the sudden flash flood from a monsoon thunderstorm surging across the Bear Creek floodplain is an awesome experience. In Fall, a brief flurry of golden Cottonwood leaves swirling to the ground along Bear Creek can cause one’s Spirit to soar. But come Winter’s cold, typically it is the magical rays of the Sun that stir one’s senses, be it those first rays of a frosty morning Sun breaking over Turtle Rock to illuminate a snow-covered wonderland, or the brilliance of the late afternoon Sun piercing through the maze of barren branches above to cast a kaleidoscope pattern of hard light and deep shadow over the floodplain path below.
This winter, the magic of the snow-covered wonderland came early Christmas morning, and for those guests who trekked out early on the trails before dawn, the magic was palpable at every turn. This was especially so down along Bear Creek where the snow created a fantasy world in high contrast black and white among the majestic trunks and tangled branches of the gnarled Gray Oak, Cottonwood, and Willow. However, on this Christmas morning, the Sun’s rays didn’t break over Turtle Rock as the clouds hung on until around ten o’clock before clearing slowly to reveal the gleaming soaring peaks of the Gila Wilderness mountains just to the north. During the following weeks, the Sun’s rays became an increasingly rare magical treat as the persistent jet stream continued to drag clouds and rain in from the Pacific, reminding the Casita hosts more and more of their seven-year sojourn in Southwest Ireland than of the normally ever-sunny Winter enchantment of Southwest New Mexico!
Heading down the Corral Road to Bear Creek with Turtle Rock beyond
Over the Creek and through the Willows leads the trail to Paradise Mountain.
But while the Sun’s rays continued to play a mostly well-hidden game of hide and seek, down below the Casitas there was a rare form of Nature’s Magic taking place for those who would care to observe … the magic of Active Change within the Bear Creek floodplain.
ACTIVE STREAM PROCESSES AND CHANGES OBSERVED WITHIN THE BEAR CREEK NATURE PRESERVE
The month-long duration of the Mid-Winter Deluge of 2016-17 provided an exceptional opportunity for interested Casita guests to observe and reach an understanding of the primary forces and processes of Nature that have acted overtime to create the Bear Creek Nature Preserve environment.
CHANGES IN STREAM CHANNELS AND FLOODPLAINS
Stream channels and floodplains, by their very nature, are environments of constant physical change in terms of shape and location (geomorphology). This is due to the constantly fluctuating volume, velocity, and turbulence of stream water flow through time that causes the erosion, transport, and deposition of the loose sediment being carried downstream. Most of the time the changes are imperceptibly slow; at other times they can be extremely rapid, causing major change in a matter of hours. During the Midwinter Deluge of 2017 the stream channels and portions of the floodplain underwent major physical change largely because of the exceptional, month-long duration of a persistent rain and snowmelt runoff event.
Stream Gradient and Base Level
As the high water continued, both the bottom and sides of the channel were eroded, undercutting the Cottonwoods on the edge of the floodplain
It is the nature of all streams, rivers, and creeks, no matter what size or where they are located, to evolve towards a state of an equilibrium where there is neither erosion nor deposition of sediment within the channel of the flowing water. Factors inherent in achieving such a balance include the variables of volume, velocity and degree of turbulence of the flowing water, plus the gradient of the stream.
Stream gradient is a term that describes the grade or slope of the stream’s surface, and is a measurement of the drop in elevation of the stream’s surface over a horizontal distance. Stream gradient is typically stated in feet per mile or meters per kilometer. High gradient streams have a steep grade with greater velocities and turbulence within the flowing water, typically resulting in erosion of loose sediment from the bottom and the degradation or cutting down of the channel bottom. Conversely, low gradient streams have less slope with slower flowing water and less turbulence that typically results in deposition of transported sediment and aggradation of the channel bottom.
Downstream at the southern end of Casita lands, as Bear Creek Canyon widens, so do the channel and floodplain, resulting in a lower gradient stream with deposition of finer-grained bed load and coarse suspended load
As the gradient of a stream approaches zero the stream is said to be approaching equilibrium at base level where all sediment transport and deposition ceases. Attainment of equilibrium along the course of a stream is rarely achieved for more than a brief span of time during periods of changing velocity or volume of water flow, exceptions being when the stream encounters a temporary base level, such as a stream flowing into a lake or reservoir. Ultimate base level is reached when a stream finally flows into the ocean.
Stream Sediment Transport
Sediment transport by running water in rivers, streams, or creeks, such as Bear Creek, occurs in two ways: as bed load where the coarse sediment (sand and gravel) maintains contact with the stream bottom by rolling, sliding, and skipping along the bottom (a process also known as saltation); and as suspended load where finer-grained sediment (sand, silt, and clay) are carried suspended by turbulence within the moving water column.
The unconsolidated fluvial sediment that makes up the channels, floodplain, and adjacent stream terraces of Bear Creek ranges from clay size particles less than 4 microns (.004 millimeters) in diameter to boulders up to 1 meter in diameter. The rate at which this sediment is transported downstream as bed load and suspended load varies greatly depending on the sediment size, the velocity and the turbulence of the moving water. In general, the larger the sediment particle, the slower it travels downstream.
As the flood waters begin to recede, a coarse deposit of cobbles and boulders bed load is deposited on a gravel bar at the side of Bear Creek while the suspended load muddying the water continues downstream
Suspended load sediment is carried downstream at the velocity of the stream, which during flood stage on Bear Creek can move at rates of up to 20 miles an hour. The size of sediment particles carried in the suspended load is dependent on the velocity of the water plus the roughness of the stream bottom due to big rocks, roots, branches, etc., along the bottom and sides of the channel which create turbulence in the water column that acts to keep the sediment suspended.
In most years, the waters of Bear Creek within the Bear Creek Nature Preserve measure a few inches in depth and only 10 to 20 feet in breadth for about ten months out of the year; the water is crystal clear, and moves downstream at speeds of only a few feet per second. During such times, sediment transport and changes in the morphology of the stream channels and the adjacent floodplain are, to the casual observer, essentially non-existent. It is only upon very close examination that movement of fine-grained sediment as bed load can be observed along the bottom.
SOME CHANGES REVEALED
During the Midwinter Deluge Event, the flow of water in Bear Creek remained high, fluctuating between just remaining within the main stream channels with depths of 2 to 3 feet to occasionally overflowing the channels by an additional 1 to 2 feet and flowing out across the floodplain. While the velocity and volume of the water during the event were elevated, it was not just the velocity or volume of the flowing water that produced the major changes observed in the Bear Creek Nature Preserve during and following the event. In this case, it was the duration of the high water event, which persisted unabated at consistently elevated levels for more than a month. This produced many dramatic changes, including:
As high water erodes banks of the channel, floodplain trees topple in the Creek diverting the course of the channel
• Significant channel modification through erosion of channel banks and diversion of stream flow by the undercutting and toppling of trees along channel margin
• Initiation of new channel development and deepening of older high water channels across the floodplain
• Massive erosion, transportation, deposition, or relocation of vast tonnages of coarse bed load and suspended load sediments
• Selective suspension and removal of sand, silt, and clay sediment from the bottom and sides of stream channels due to high level turbulence within the fast moving water. Under these conditions, once this sediment was suspended it was carried downstream out of the Bear Creek Nature Preserve leaving behind channels that have been cut deeper by one to several feet and filled with coarse gravel and boulders.
As floodwaters leave the channel and flow across the floodplain, new channels are cut, such as in this photo with the old channel on the right and the new channel that was started at high water on the left
With only a few more floods, this new channel being cut into the floodplain will soon become the main channel; note the massive amounts of bed load and suspended load left behind by the receding waters
By early February 2017, the flood waters had dropped significantly, revealing the active Bear Creek channel cut down about 2 feet with the sides and bottom lined with large coarse gravel, cobbles, and boulders deposited from the bed load; the sand, silt, and clay sediment having been selectively removed from the channel as suspended load and carried away downstream
A MID-WINTER DAY’S SEARCH FOR CHALCEDONY AND FIRE AGATE
AT ARIZONA’S BLACK HILLS ROCKHOUNDING AREA
Fire-agate and chalcedony collected at Black Hills Rockhound Area
THE SOUTHWESTERN NEW MEXICO AND SOUTHEASTERN ARIZONA BORDER COUNTRY
– A ROCKHOUNDER’S PARADISE
The three physiographic regions of Arizona: Colorado Plateau Region, Mogollon Rim Transition Zone which includes the Mogollon-Datil Volcanic Field, and the Basin and Range Province (Wikimedia Commons: Mortadelo 2005)
The Southwestern New Mexico and Southeastern Arizona Border Country offers some of the finest and most diverse rockhounding opportunities to be found anywhere in the Southwest. Semi-precious gems, minerals, and rocks of an extremely wide diversity can be found here, including white to pink chalcedony, fire agate, banded agate, red and yellow jaspers, carnelian, obsidian, geodes and thunder eggs, and banded rhyolites, as well as exotic copper minerals like turquoise, malachite, azurite, and chrysocolla. These are but a few of the treasures that can be hunted and collected here, scattered over the surface on many thousands of acres of public lands, as well as excellent specimens that can be dug from the tailings dumps at numerous abandoned gold, silver, and copper mines that operated in the late 1800s and early 1900s.
The reason for this great abundance and diversity of collectable rocks and minerals is that the Southern New Mexico-Arizona border straddles a complex geological transition zone encompassing the eastern edge of the Basin and Range Province and the southwestern side of the Mogollon-Datil Volcanic Field at the southern end of the Colorado Plateau. During the Oligocene and Miocene Epochs of the Mid-Tertiary Period between 35 and 15 million years ago, this vast area in the American Southwest was the site of repeated episodes of extensive faulting, vulcanism, and extensive mineral vein intrusion, each of which are critical factors favoring the formation of unique and desirable specimens sought by the avid rockhound. Situated just 30 miles east of the New Mexico-Arizona border, Casitas de Gila Guesthouses is located in the heart of this rockhounding paradise. As such, no matter which direction one takes from the Casitas on a single day’s outing, there are excellent collecting sites to be discovered.
FIRE AGATE: THE PREMIER SEMI-PRECIOUS GEMSTONE
OF THE SOUTHERN NEW MEXICO-ARIZONA BORDER COUNTRY
An exceptional piece of high grade fire agate in the rough from Slaughter Mountain, AZ, showing beautiful fire agate just beneath an enclosing layer of semi-transparent chalcedony (Wikimedia Commons: Maricopa Mining LLC )
One of the semi-precious stones most highly sought after by rockhound guests staying at the Casitas is fire agate. Fire agate is a type of chalcedony (SiO2) which contains multiple, extremely thin layers of the iron oxide minerals of Goethite (FeO(OH)) and Limonite (FeO(OH)·nH20) imbedded within, and commonly completely enclosed by, semi-transparent to translucent layers of cryptocrystalline chalcedony. When cut and polished down to the layers containing the iron oxides, the stone displays a metallic, shimmering iridescence known as the Schiller Effect, where light is reflected and refracted off the various layers containing the Goethite and Limonite iron oxides to give the exquisite play of colors—or “fire”—for which the gemstone is named. Colors displayed by the “fire” vary greatly, the most common being shades of orangish brown, but also all shades and tones of yellow, orange, red, and green, and more rarely, purples and blues.
Semi-transparent and translucent chalcedony as collected at Black Hills Rockhound area February 10, 2016
Pure chalcedony, while composed of only cryptocrystalline SiO2, is actually a very fine intergrowth of two separate minerals, quartz and moganite, which have the same chemical composition but differ in their crystal structure. In the New Mexico-Arizona border country, chalcedony is typically found in shades of translucent white to pink and light grays and blues. It commonly displays a waxy luster and botryoidal texture.
HOW FIRE AGATE AND CHALCEDONY FORM
The fire agate and chalcedony of the Southern New Mexico–Arizona border area is formed when low pressure and low temperature epithermal hydrothermal waters (50°-200°C / 122°-392°F) carrying colloidal SiO2 and iron oxides are injected into cavities in volcanic rocks such as gas bubbles in flow rocks, irregular-shaped vug fillings, or along fault or bedding plane fractures. Deposition of the chalcedony can take place by the slow buildup of numerous thin layers over an extended time from watery fluids, or rapidly all at one time from viscous silica gels, which appear to have had a viscosity of tooth paste … an extremely hot tooth paste! The May 27, 2014 Blog “Seeking Chalcedony and Jasper in Southwest New Mexico” includes numerous photos on the various forms and shapes of chalcedony and fire agate that have been found at or near the Casitas over the years, and presents more details on their various modes of formation.
A DAY TRIP OF COLLECTING AT THE BLACK HILLS ROCKHOUND AREA
The Black Hills Rockhound Area is located in Arizona, 50 miles west of Casitas de Gila Guesthouses, just off US Highway 191, about 13 miles west of the crossroads community of Three Way and 19 miles east of Safford, Arizona. The site is a designated rockhound area on BLM (U.S. Bureau of Land Management) land, and is open to the public year round.
A BEAUTIFUL EARLY MORNING DRIVE OVER THE HIGH CHIHUAHUAN DESERT MOGOLLON-DATIL VOLCANIC FIELD TO THE SONORAL DESERT BELOW
The drive from the Casitas to the Black Hills Area takes about 1.5 hours, traveling on excellent highways that pass through some of the most scenic mountain country in Southwestern New Mexico and Southeastern Arizona. From the Casitas, the route goes northwest on US 180 through a High Chihuahuan Desert landscape affording magnificent views of the Mogollon Mountains before turning west on NM 78 through the incredibly beautiful Mule Creek Country.
Looking east to the Mogollon Mountains in the Gila Wilderness across the rolling grassland of Mule Creek Country just off State Road 78
Notable for having some of the finest ranch land in Southern New Mexico, the Mule Creek area is a mile-high landscape of rolling grasslands offset by a sparse scattering of Alligator Juniper trees. After passing through the tiny community of Mule Creek — don’t blink or you’ll miss it! — the road immediately enters the Gila National Forest where it begins a gradual six-mile climb over the northern extent of the Burro Mountains before crossing into Arizona and entering the Apache National Forest at an elevation of 6,000 feet.
Looking southwest across High Sonoran Desert from the overlook on State Road 78, 5.6 miles into Arizona from the New Mexico-Arizona border. From this overlook at an elevation of 6,250 feet the road descends 2,650 feet over the next 14 miles to the small community of Three Way, Arizona, on the Gila River. The 10,696-foot peak of Mt. Graham commands the center skyline 52 miles in the distance.
For the next 5.6 miles the road winds through a Ponderosa-shaded mountain roadway within the Apache National Forest before reaching an amazing overlook and parking area at the edge of a major topographic, physiographic, geologic, biologic, and ecologic boundary that marks the abrupt transition from the southwestern extent of the High Chihuahuan Desert of the Mogollon-Datil Volcanic Field into the eastern edge of the High Sonoran Desert of the Basin and Range Province. The westward view from this overlook affords a marvelous long-distance view into the Sonoran Desert Country within the Basin and Range Province of Arizona, with the 10,696 foot towering presence of Mt. Graham looming 52 miles to the west.
Leaving the lookout parking area at an elevation of 6,250 feet, the highway descends rapidly through a series of switchbacks and a distance of 4 miles some 1,200 feet down the face of a west-facing escarpment, leaving behind the flora and fauna of the High Chihuahuan Desert and entering the totally different natural world of the High Sonoran Desert. Upon reaching the base of the steep escarpment, Highway 78 continues a downward but more gradual descent of another 1,400 feet in elevation over the next 10 miles to arrive at Three Way, Arizona, at elevation of 3,600 feet. The change in landscape, both topographically, geologically, biologically and ecologically over this 14 mile stretch of highway is both dramatic and amazing and for most travelers will be remembered as one highlight of the day’s journey.
Entrance sign at U.S Highway 191 for BLM’s Black Hills Rockhound Area
At Three Way, Highway 78 ends and the journey continues straight ahead on U.S. Highway 191 to once again cross the Gila River and for the next 13 miles passes through a fascinating Sonoran Desert landscape of weathered and dissected volcanic hills, mountainous ridges, mesas, and sharp pinnacles or buttes, almost all of which is public BLM or State of Arizona land. At mile marker 141.6, a sign on the right (north) side of the road marks the entrance road to the Black Hills Rockhound Area.
Turning in off the highway, a well-maintain gravel road is followed for two miles to a parking area where another sign informs the visitor that they are at the center of the Black Hills Fire Agate deposit, and further states that while small pieces of fire agate can be found on the surface, large pieces will have to be dug for! Translation of BLM wordage: “the big pieces have already been picked up by somebody else before you got here.” But don’t be put off: there are still tons of collectable material out there … somewhere!
THE FIRE AGATE AND CHALCEDONY OF THE BLACK HILLS ROCKHOUND AREA
Every year during the Summer Monsoon Season intense thunderstorms expose, transport, and deposit new fire agate and chalcedony for collecting as heavy rain runoff rushes down from the higher regions of the Black Hills Rockhound Area to the lowlands below
Looking west from the prominent ridge on north side of fire agate deposit towards the parking area at Black Hills Rockhound area in center of photo, 2 miles in from US Highway 191
The Black Hills Rockhound Area is one of two designated fire agate localities on BLM land in Southeastern Arizona, the other being the Round Mountain Rockhound Area, some 27 miles to the southeast near the Arizona-New Mexico border. Both of these areas are well known and receive many visitors each year. Because of this, one might wonder if there is any material left to be collected. Actually this is not a problem for two reasons: the first being that the area at the Black Hills site where fire agate and chalcedony can be found is vast, comprising thousands of acres of public BLM land surrounding the main collecting area, some of which comprises incredibly rough and steep terrain which is rarely visited. The second reason is that because of the heavy rainfall the area receives during the annual Summer Monsoon thunderstorm rains, which can exceed 2 to 3 inches in a half hour, fire agate and chalcedony buried beneath of surface of the ground is constantly being uncovered and exposed by high energy flash flood runoff every year. Proof of this process of replenished collectable material is the fact that over the past 18 years no Casita guests visiting the area have ever returned empty handed!
Are some areas better to look than others? Of course! And in that respect, rockhounding is much like fishing:. experience and understanding of the quarry counts! And so, it is in that context that the following brief geologic overview is offered as an aid to knowing where to look for the Black Hills fire agate and chalcedony. After reading this, however, it must always be kept in mind when setting out for a day of rockhounding, that just like it is in fishing, there will always be the occasional great day, many good days, and those other days where, well, it was certainly a nice day for being out in the desert connecting with nature! But, then, isn’t that at least half of the fun anyway?
A MODICUM OF UNDERSTANDING REGARDING THE SUCCESSFUL SEARCH FOR AND RECOVERY OF THE RECLUSIVE AND ELUSIVE FIRE AGATE AND CHALCEDONY OF THE BLACK HILLS ROCKHOUND AREA
Close up of pyroclastic rhyolite ash fall welded tuff bedrock forming massive resistant cliffs at east end of ridge north of parking area
Outcrop of broken angular blocks of andesite bedrock showing abundant gas bubbles near west end of ridge east of parking area. The large cactus is the Barrel Cactus, a common plant of the High Sonoran Desert.
The geology of the Black Hills Area is not very complex. Basically, there are two main volcanic rock types of Mid-Tertiary age (Oligocene to Middle Miocene or 30 to 15 million years ago) which make up the bedrock that crops out at the surface on the tops of the hills, ridges, and small mountains that surround the Black Hills parking area. These rock types consist of 1) dark gray to reddish gray andesite lava flow rock that is deposited in a sequence of essentially horizontal layers, many of which contain abundant gas bubbles, and 2) gray to light tan, silica rich, rhyolite pyroclastic ash flow or ash fall welded tuff that overlies or is interbedded with the andesite flow rock. The andesite flow rock is the host rock for the fire-agate and chalcedony which, as explained above, forms over time through secondary deposition from hydrothermal waters containing colloidal silica and iron oxide colloids that slowly fill or are injected into cavities such as gas bubbles, irregular shaped vugs, and thin veins within the andesite flow deposits. In most cases the overall volume percentage of chalcedony and fire agate that forms within the flow rock is extremely small — much less than 1%, although examination of the vertical sequence of the Black Hill andesite deposits does show that certain layers or levels do contain more void space and hence higher concentrations of chalcedony and fire agate than others.
Both andesite and rhyolite ash fall welded tuff bedrock occur along the top of the ridge north of parking area. In this photo weathered and disintegrating blocks of andesite comprise the foreground on left, and the high promontories on far right horizon, and rhyolite welded tuff constitutes the cliffs in middle distant horizon.
Massive cliffs and large broken blocks of andesite flow rock and rhyolite welded tuff bedrock comprise the tops of a low ridge lying about a half mile to the north of the designated parking area in the center of the Black Hills Fire Agate area. On the sides of this ridge, below and surrounding the solid rock outcrops, are loose accumulations of smaller broken rock, coarse rock debris, and soil that is in the process of being carried downslope from the rock outcrops.
Andesite is composed of a high concentration of feldspar and other minerals which over time will break down physically and chemically decompose to form an unconsolidated mineral soil of clay minerals and fine rock particles, thereby releasing the contained fire agate and chalcedony which retains its original size and shape because SiO2 minerals are very stable and inert to weathering and chemical decomposition at the Earth’s surface.
Following this breakdown of the andesite bedrock, the processes of gravity, wind (desert pavement), and running water in the form of flash floods, acting over thousands of years, will carry the altered and disintegrated clay particles, fine rock debris, and the fire agate and chalcedony further and further downslope and away from the bedrock to be redeposited in and over the surrounding lowlands, flats, valleys, and washes.
As weathering of the andesite bedrock continues over time, the bedrock and large blocks of andesite found higher up on the ridge are broken down into smaller and smaller pieces and loose mineral soil which are gradually transported further and further downslope by Monsoon rain runoff. Here, on the lower slopes well below the ridge east of the parking lot an abundance of Prickly Pear Cactus indicates the presence of an increased percentage of fine sediment and mineral soil plus accompanying retention of ground moisture. Note also the numerous small white rocks in the foreground. These are pieces of white chalcedony that also become concentrated on the lower slopes through the breakdown of the andesite bedrock.
Gradually, this process will produce a thick, wedge shaped deposit of successive layers of transported sedimentary material surrounding the bedrock core of the ridge. Since the clay and finest rock particles are selectively carried furthest away by the periodic flash flood runoff from the source bedrock upslope, a concentration or lag deposit of the larger rock fragments and, of most interest to rockhounds, the physically and chemically inert pieces of chalcedony and fire agate, accumulates over the ground surface following each successive flash flood coming off the surrounding the uplands. Successive floods will, of course, bury previously deposited layers of the concentrated fire agate and chalcedony as the erosion of the bedrock upslope on the ridge continues and the wedge shaped deposits surrounding the ridge thicken.
The important result of this process is, of course, that the concentration of fire agate and chalcedony which was less than 1% in the original solid host rock may now be increased many times over in the loose, unconsolidated sediments and mineral soil, which in addition to being picked up on the surface can be successfully recovered by digging with pick and shovel.
Naturally, the big question of course is: Where does one dig? Hopefully, the above discussion offers some clues as to where to begin, and your hosts at the Casitas will be pleased to offer additional suggestions if asked. However, it must be kept in mind that it is this very same question that has perplexed every prospector in the American Southwest for over a hundred years, and in most cases it is only after much personal experience and perseverance that Mother Nature will even consider beginning to answer the question. So in the meantime, good luck in your quest and enjoy the chase!
On the hunt for the reclusive and elusive fire agate amongst the Ocotillo and Prickly Pear Cactus at Black Hills Rockhound area
A welcome lunch break in the shade of the rhyolite welded tuff cliffs at the top of the ridge
A “DAY’S CATCH” AT THE BLACK HILLS ROCKHOUND AREA
As further proof that there is still lots of good fire agate and chalcedony to be found at the Black Hills Rockhound Area, the following photos represent the best of the “Day’s Catch” over a four-hour period by your Casitas’ hosts on a beautiful early Spring day in February 2016.
A large piece of fire agate encased in translucent chalcedony
No two pieces of fire agate in the rough are the same
Only through grinding and polishing of this fire agate in the rough can the underlying beauty be revealed
Fire agate is often encased in thick layers of semi-transparent to opaque chalcedony
Pure chalcedony can take on a variety of shapes and forms, such as this strange frog-like little creature perched on this fragment of weathered andesite¬
We’re taking a break from the Gila Nature Blog for a few months in order to focus on other projects. Since January 2011, when the first Blog article appeared, a wide range of topics has been covered. Here’s a summary of several topics. If your favorite topic isn’t listed below, use the panel to the left to find your interests.
We look forward to having you as a guest at Casitas de Gila Guesthouses!
HIKING AT THE CASITAS
• Hidden Spring Trail — January 2011
• Dry Wash Trail — October 2014
• Paradise Overlook Trail — February 2015
HIKING IN THE AREA
• Turkey Creek Hot Springs Trail — April 2011
• Mineral Creek — February 2012
• The Catwalk & The Gold Dust Trails — April 2012
• Middle Box of the Gila — June 2012
• Mogollon Box Trail — July 2012
• San Francisco Hot Springs Trail — September 2012
• Lower Little Dry Creek Canyon — April 2013
• A Fall Hike — October 2013
• Upper Little Dry Creek — November 2013
• Mineral Creek in the Winter — January 2014
• Sacaton Creek – November 2014
• Sheridan Corral Trail — May 2015
• Rain Creek Canyon – July 2015
• Volcanoes — March 2011
• Obsidian – August 2012
• Fluorite – May 2013
• Chalcedony & Jasper – May 2014
• Mineral Creek – February 2012
• Coronado – December 2012
• Apacheria (Part 1) – February 2013
• Apacheria (Part 2) – March 2013
• Ancient Crops – August 2013
• San Francisco River Back Country – February 2014
• Gila Cliff Dwellings (Part 1) – August 2015
• Gila Cliff Dwellings (Part 2) – September 2015
• Billings Vista Birding Area – June 2012
• Winter & Spring Birding – April 2014
SOME OBSERVATIONS OF THE EFFECTS OF THE EL NIÑO / LA NIÑA
CLIMATIC OSCILLATION CYCLE WITHIN THE BEAR CREEK NATURE PRESERVE
AT CASITAS DE GILA GUESTHOUSES
El Niño Winter of 2015-16: Fresh snow on the Pinos Altos Range in the Gila Wilderness, five miles north of Casitas de Gila
CLIMATIC AFFECTS OF EL NIÑO AND LA NIÑA WINTERS ON SOUTHERN NEW MEXICO
Historical records show that El Niño winters in the Southwest are marked by increased precipitation and warmer temperatures, while La Niña winters are marked by decreased precipitation and colder temperatures. During El Niño years, moisture-laden low pressure systems coming in off the Pacific Ocean tend to follow a southern route, carried along by the west-to-east flow of a persistent Pacific Jet Stream across the Southwest and into southern New Mexico (see Figure 1 below.) During La Niña years, however, eastward-moving, moisture-laden low pressure systems coming in off the Pacific Ocean tend to take more northerly routes across the western U.S., carried along by the west-to-east variable flows of the Pacific and Polar Jet Streams, bringing dry, sunny high pressure conditions to prevail over the Southwest and New Mexico.
FIGURE 1: Schematic drawing showing climatic weather patterns of La Niña and El Niño for North America. Prepared by NOAA/ National Weather Service/ National Centers for Environmental Prediction.
MONITORING OSCILLATIONS OF EL NIÑO AND LA NIÑA BY THE OCEANIC NINO INDEX (ONI)
Sea surface temperatures fluctuate constantly in the Central Pacific along the equator, and when monitored and averaged over time demonstrate repeated oscillations between El Niño (warm) and La Niña (cold) episodes. The U.S. National Oceanic and Atmospheric Administration (NOAA) monitors these oscillations by averaging monthly measurements of surface sea water temperatures collected over an area that covers the central portion of the Pacific Ocean between 5°N and 5°S latitude and 120° to 170° W longitude. These temperature fluctuations, when averaged over successive three-month intervals during the year (which NOAA refers to as “seasons”), yield temperature anomalies that NOAA calls the Oceanic Niño Index (ONI). ONI values generally lie within 3°C of the average temperature for any given area at any specific time of the year. Anomalies that deviate from the average temperature in excess of +0.5°C mark a shift towards a warm El Niño episode, whereas anomalies in excess of -0.5°C mark a shift towards a cold La Niña episode. Anomalies that are between ±0.5°C are called a Neutral Episode, or, as they are sometimes humorously referred to, a La Nada episode. By NOAA’s definition, an El Niño or La Niña episode can only be so named when the average of three consecutive ONI three-month seasonal values exceed the ±0.5°C threshold.
CYCLES OF EL NIÑO AND LA NIÑA FOR NORTH AMERICA 1950 to 2015
When plotted through time as shown in Figure 2 below, it is very clear that El Nino and La Nina episodes are predictably cyclic in nature, with an average duration between 3 and 4 years. Although these episodes do show variability in both duration and intensity, they are not unusual in any way, and are just another of Nature’s cycles that has a pronounced affect upon the natural environment and plant and animal populations in the American Southwest.
NOAA graph showing 65 years (1950 to 2015) of El Niño (red) and La Niña (blue) cycles
THE TRANSITION OF THE RECENT LA NADA EPISODE OF MARCH 2012 TO EARLY 2015 INTO THE VERY STRONG EL NIÑO OF 2015 – EARLY 2016
As can be seen in the Oceanic Niño Index, the American Southwest entered a Neutral or La Nada episode beginning around March of 2012. This La Nada episode continued throughout the rest of 2012, 2013, 2014, and into the first two three-month monitoring periods of 2015. However, beginning in the third three-month interval of February/March/April 2015, the ONI shows a weak El Nino episode gradually strengthening throughout the year to become a very strong El Nino episode by December 2015. Current projections (.pdf file) as of January 4, 2016, have the strong El Niño conditions continuing throughout the rest of the 2015-16 Winter, followed by a slow transition into an ENSO Neutral episode or La Nada situation by Late Spring or Early Summer.
PRECIPITATION DATA COLLECTED AT CASITAS DE GILA ILLUSTRATE THE TRANSITION OF A PERSISTENT LA NADA EPISODE TO A STRONG EL NIÑO EPISODE BETWEEN MARCH 2012 and DECEMBER 2015
Precipitation at Casitas de Gila has been monitored electronically on a daily basis for many years. Some of this data is presented in Tables 1 and 2 below. Examination of this precipitation data illustrates the transition of a persistent La Nada episode to a strong El Niño episode between March 2012 and December 2015.
As can be seen in Tables 1 and 2, there is a marked increase in precipitation from 2012 to 2015, on a yearly total basis and also when comparing Fall and Winter month totals. The NOAA projection for the Oceanic Niño Index (ONI) for the remainder of the 2015–16 Winter is to remain in an El Niño episode, returning to a Neutral or La Nada episode in Late Spring or Early Summer. If this projection holds true, the Fall and Winter total precipitation should exceed the 2014-15 total precipitation.
SOME OBSERVED POSSIBLE AFFECTS OF THE TRANSITION OF THE LA NADA EPISODE OF 2012 TO 2015 INTO THE STRONG EL NIÑO EPISODE OF 2015 UPON THE FLORA AND FAUNA OF THE BEAR CREEK NATURE PRESERVE AT CASITAS DE GILA
Casitas de Gila is situated on the western edge of Bear Creek Canyon about 80 feet above the Creek overlooking the 265 acres, 3/4 mile of Bear Creek, and 6 miles of trails that constitute the Bear Creek Nature Preserve.
During the time period from March 2012 and December 2015, various changes have been observed in the flora and fauna of the Bear Creek Nature Preserve at Casitas de Gila Guesthouses which may be in response to the transition from the La Nada episode to a very strong El Niño episode as documented in Tables 1 and 2. Some of these observations are presented below. In considering these observations, it must be stressed that they are the result of long-term, daily, on-site personal observations only, and not the conclusions of a rigorous scientific study. It is also important to remember the important principle that must always be kept in mind when dealing with any study of Nature, namely: that “Correlation does not necessarily equate to Causation”. With those caveats stated, the following possible affects of the transition of the La Nada episode of 2012 into the strong El Niño of 2015 are presented:
OBSERVED TRENDS IN FLORA AT THE BEAR CREEK NATURE PRESERVE 2012 to 2015
The marvelous Doubting Mariposa Lily (Calochortus ambiguus) found blooming on April 25, 2015, at Casitas de Gila as a result of the 2014-15 El Nino Winter moisture; this is the first time this flower had been observed at the Casitas
• During and in the months immediately following the very dry year of 2012 (total precipitation 6.86 inches), and cold Winter of 2012-13, flowering and seed production of trees, shrubs and grasses at the Casitas were much below normal. Numerous individual plants of several species, such as the Turpentine Bush (Ericameria laricifolia) and Engelmann Prickly Pear (Opuntia engelmannii), on the Casitas’ Self-Guided Nature Trail were observed to die. Spring flowers in particular were notably absent.
• As yearly and Fall/Winter precipitation steadily increased during the transition from La Nada to El Nino, flowering and seed production likewise increased, culminating in the Spring of 2015 when a profusion of flowers occurred over the Casita lands. So profuse and obvious was this prolific flowering of diverse species (some of which had not been seen in many years, and others, such as the Doubting Maricopa Lily (Calochortus ambiguus), had never been observed or recorded previously at the Casitas), that it became the subject of two Nature Blogs in March and April of 2015.
OBSERVED TRENDS IN FAUNA AT THE BEAR CREEK NATURE PRESERVE 2012 to 2015
The Whitewater-Baldy Fire on May 22, 2012, 25 miles in the distance as viewed one mile from the Casitas
• 2012 was a year of severe drought and a very difficult time for animals both at Casitas de Gila and at the adjacent Gila National Forest and Gila Wilderness. This was also the year of the Whitewater-Baldy Complex Fire which became the largest forest fire in New Mexico’s recorded history.The fire started on the west side of the Mogollon Mountains just within the Gila Wilderness about 25 miles northwest of Casitas de Gila on May 9, 2012, when two dry-lightening strikes touched off the drought-parched forest. The resulting conflagration was finally declared controlled on July 31, after burning some 297,000 acres of the 600,000 acres of the Gila Wilderness, at an estimated cost of $100 million dollars. This incredibly destructive fire was the subject of a Nature Blog in September 2013.
The combination of the Whitewater-Baldy fire and the ongoing drought of 2012 resulted in some expected and unexpected changes in animal populations and occurrences within the Bear Creek Nature Preserve.
• With the lack of Spring rains in 2012, stock tanks in the mountains adjacent the Bear Creek Nature Preserve dried up early and normal Spring grass and shrub vegetation in the uplands was deficient to completely lacking. Consequently, Bear Creek in front of the Casitas (which always has water in it year around) saw an increase in animals, both large and small, as it was the only source of water and food around. Some of the increase was probably also due to animals fleeing the Whitewater-Baldy Fire in the adjacent Gila Wilderness. Black Bear, Rocky Mountain Bighorn Sheep, and Mountain Lion (the only predator of the Bighorn Sheep) sightings at the Casitas and on Bear Creek were up. Adult Bighorn populations seemed normal; however, only two newborn lambs were observed during 2012 at any one time on the cliffs following lambing in Late Spring. In June a mother Black Bear brought her two cubs to Bear Creek for food and water, and for the first and only time in the 18 years history of the Casitas, garbage cans were raided by the bears.
• In 2013 and 2014, precipitation increased as the overall climate moved towards the El Niño episode. In the early morning hours of September 22, 2014, the largest flash flood ever recorded at Casitas de Gila in its 18-year history occurred when the remnants of a major hurricane in Baja California triggered a series of thunder storms traveling down the Bear Creek drainage from its headwaters in Pinos Altos, creating a flood crest of 12 feet above normal Creek level. The effect of this flood upon less-mobile animals, such as reptiles and amphibians, was undoubtedly devastating, as their observed populations were significantly less in succeeding months.
Most other animals were observed to prosper during 2013 and 2014. During this time the frequency and count of both Bighorn Sheep and Mule Deer sightings increased in 2013, with five Bighorn lambs observed in Late Spring. No Bighorn lambs were observed or recorded in 2014, however.
• In 2015, the El Niño episode arrived with the greatest total yearly rainfall in four years. It was a year of relative plenty in terms of both food and water for all animals, big and small. Bighorn sightings increased with up to 16 individuals observed at one time, 5 of which were lambs. Mule Deer sightings were also up in frequency and count number. Small animals such as Rabbit (both Cottontail and Jackrabbit), Gray Fox, and Field Mice appeared to be much more abundant than in previous years. By the end of the year the Gray Fox population obviously had boomed, based on the amount of scat observed around the Casitas. The chipmunk population, however, was noted as having greatly declined by the end of 2015. Mr. and Mrs. Fox? Most likely.
When all of these various observations are considered together, it is clear that the climatic impact of the La Nada to El Niño transition upon plant and animal populations and the overall food chain during the cyclical transition from the 2012 drought to abundant precipitation in 2015 is definitely mirrored in the observed cycles of plant and animal population and reproduction variability. Some of these cyclical changes are obvious, others only suggested. What is certain, however, is that the overall ecology of the Bear Creek Nature Preserve provides a unique opportunity to observe first-hand the eternal cycles of Nature on a micro-scale for those who have the patience to observe, study and learn.
El Niño Winter of 2015-16. Fresh snow on the Mogollon Range in the Gila Wilderness, 10 miles northwest of the Casitas