Keywords and Themes

Concepts: base level, relief, tectonic thinning, interior drainage Structural features: Basin and Range, Faults (normal fault, listric fault, strike slip fault) pull-apart basin, fault block mountain (horst), fault block basin (graben), fault scarp, faceted spurs Other Geologic Features : Playa, alluvial fan, bajada, alkali spring, pluvial lake, salt pan, evaporite, Pluvial Lake Manly, Shoreline Butte, Badwater , wineglass valley (DB image), turtlebacks Economic Deposits: borax minerals, gold and silver Volcanic Features: basaltic cinder cones, maars, and Ubehebe craters

Objectives

• Explain why Death Valley is the driest and hottest place in the United States.
• List and describe the three factors that most strongly influence Death Valley's landscape.
• Describe the structure and evolution of the physiographic province containing Death Valley.
• Explain why the rocks of Death Valley exhibit greater deformation and metamorphism than similar aged rocks on the Colorado Plateau.
• Distinguish between joints and faults.
• Explain the difference between normal, reverse, and strike slip faults, and identify the type of faulting that is currently occurring across the Basin and Range.
• Discuss how Death Valley differs from the Grand Canyon in shape, dimensions and manner of formation.
• Explain the difference between an interior and exterior drainage system.
• List and describe at least 3 geomorphic features typically found in an interior basin like Death Valley.
• Describe badlands topography and the conditions that produce it.
• Explain how geomorphic features such as faceted spurs and wineglass (or hourglass) valleys area formed by normal faulting.
• Identify and explain the formation of alluvial fans.
• Site two feature of recent volcanic activity and explain why volcanic activity occurs in Death Valley.
• Explain the formation and economic value of evaporite deposits.
• Explain what originally attracted people to Death Valley given the harsh conditions of the area.
• Name and describe the pluvial lake that occupied Death Valley during the Pleistocene.

Death Valley

Death Valley is the hottest, driest, and deepest interior basin in the United States.  The valley lies in the rain shadow of the Sierra, Argus and Panamint mountains, which intercept nearly all the moisture carried east from the Pacific. Temperatures often reach 120°F, and the average annual precipitation hovers around 1.5 inches per year. In 1849, the year of the gold rush, immigrants traveled westward in search for gold, adventure, and a better life.  After a harrowing ordeal descending down the Green River, William Lewis Manley and his companions left the river and joined a small wagon train traveling southwest. The group came upon an unbearably hot desert valley, barren of life and rimmed with nearly impenetrable mountains. The valley floor was covered with dunes, saltpans and and shallow lakes of "badwater".  After several weeks of hardship, and on the brink of starvation, the party finally found a western pass though the mountains.   Manly's parting words were "Good bye Death Valley"--an appropriate name for such a desolate and inhabitable region.

Death Valley is not a meandering stream-carved valley like the Grand Canyon, but rather a linear fault valley subsiding along a arcuate normal fault.   The 120-mile long valley would be two miles deeper if it weren't for the tremendous quantities of sediment shed into it from surrounding mountains.  Fortunately, the rate of faulting exceeds the rate of infilling or this dramatic park landscape would not exist.  The three factors that most strongly influence the park's landscape are its active tectonic setting, extreme aridity, and interior drainage.

During the Mesozoic and into the Early Cenozoic a subduction zone along west coast brought in an array of volcanic islands and crustal fragments that collided with, and accreted to the western margin.  Mountain building events, such as the Nevadan, Sevier, and Laramide orogenies, resulted from these collisions. In Death Valley limestones were turned to marble, shales to slates, and sandstones to quartzites.  The now active normal faults, created by recent and on-going Basin and Range extension, cut across rocks that were compressed and stacked by collision-related thrust faulting.  Subduction eventually halted when North America over-rode the eastern-most portion of the East Pacific Rise.  The long period of compression was followed by the recent relaxation and extension. The zone of mantle upwelling that once lay beneath the ocean, now lies beneath the Basin and Range and is tearing it apart.

The geology of Death Valley is similar and yet very different from what we've seen in previous parks. The Precambrian and Paleozoic history of Death Valley is not that different from the Grand Canyon. (Compare Grand Canyon Time and Death Valley Time.) Both regions are underlain by 1.7 billion-year-old metamorphic and igneous rock. Both contain sedimentary strata laid down on the Cambrian-through-Paleozoic passive continental margin of western North America.  However, Death Valley was further west in a deeper region of the ocean. So when shoreline beach deposits or offshore muds were accumulating around the Grand Canyon, deep-water carbonates were blanketing the region around Death Valley.  What later followed shaped the different character of these western parks.  Death Valley was in the forefront of the Sevier Orogeny--exposed to collisional events along the west coast throughout the Jurassic and Cretaceous periods. Its strata were folded and stacked by thrusting faulting, and then later during the Cenozoic Era were torn apart by extension. The tall mountains that formed during the Sevier Orogeny collapsed into fragmented mountainous ridges separated by broad fault-bound valleys.  Unlike the relatively undisturbed sedimentary rocks of the Colorado Plateau, Death Valley's rocks exhibit the folding, fracturing and metamorphism inherent in a severely deformed terrane. 

 A Landscape formed by faulting

Death Valley is just one of many fault-bound basin in the Basin and Range Province. Faults are deep breaks in the earth's crust where rocks have shifted.    They develop when brittle rocks are subject to either compressional, tensional, or shear stresses. The three principle faults created under each condition are illustrated in figures 2-4.  Death Valley is actually the result of a complex interplay between shear and tensional forces (fig. 9) that have formed a pull-apart basin.

Figure 2. Cross-section of strata faulted by tensional stress.   The block over the fault (hanging wall block) moves down relative to the underlying block.  This type of fault is call a normal fault.   Normal faults are responsible for the fault block basins and mountain in the Basin and Range.	Figure 3. Cross-section of strata faulted by compressional stress.   The block over the fault (hanging wall block) moves up relative to the underlying block.  This type of fault is call a reverse fault and results in crustal thickening and shortening. The Rocky Mountain uplifts are bound by reverse faults.

Figure 4.  Surface view of a road offset by a strike-slip fault produced by horizontal shear.   The San Andreas Fault that forms plate boundary between the Pacific and North American plates is a strike-slip fault.  Strike-slip faults are also common in the Basin and Range.

Evolution of the Basin and Range and Death Valley

Around twenty million years ago, termination of subduction put a halt to collisional activity and changed the regional stress pattern. Shear and tensional forces took over and the western U.S. started breaking apart into giant fault blocks (fig. 5).  This event marks the beginning of the Basin and Range Province. Prior to this time the province did not exist. Extensional faulting continues today. Death Valley is a relatively young addition to the to province.

Geologists estimate that crustal stretching and thinning has widened the province, from the Sierra Nevadas to the Rocky Mountains, by nearly 100%.  At mid-crustal levels, where pressure and temperature are high, rocks flow when stretched and thinned.  However, in the brittle upper crust extension is accommodated by listric normal faults, a type of normal fault that flattens at depth, allowing blocks to slide horizontally like a deck of cards spread on a table (fig. 5).  The upward-tilted edge of each block forms a mountain range. The intervening lows are the basins, which are eventually fill with thousands of feet of sediment.  Deposits include layers of evaporites, muddy lake deposits, volcanic ash, fluvial gravels, and debris flow fanglomerates.  Each layer represents an event or fluctuation in prevailing conditions.

One could argue that Death Valley is the most tectonically active landscapes in the conterminous United States.  The youthful central valley is a pull-apart basin (fig. 8) created over the last 3 million years.  The Valley is a down-dropped fault block, or graben, and the flanking mountains are up thrown blocks called horsts (image).  The total vertical displacement along the Death Valley Fault Zone is over 4 miles.  However, two miles of basin fill has reduced the total relief to around 2 miles, from the tallest peak (Telescope Mt.  11,049 ft) to the lowest basin (Badwater, -282').  Active strike-slip and normal faulting is evidenced throughout the park by offset cinder cones, alluvial fans and stream deposits. 

Geomorphic Features related to faulting

Features formed by faulting, such as fault scarps, faceted spurs (fig. 6), offset valleys, wineglass valleys (fig. 7), and turtleback mountains (fig. 8) are all found in Death Valley.  Spurs are ridge divides between streams. Where they have been truncated by faulting--they form triangular facets that face the valley (fig. 5).  A wineglass-shaped valley is V-shaped with an narrow lower canyon. Such valleys reflect periodically rapid rates of uplift (fig. 7).   Turtlebacks are dome-shaped structural features cored by Precambrian rock that are unique to Death Valley.  They are formed when the overlying rocks slide off along low-angle (listric) normal faults.

Figure 6. Faceted spurs along the fault scarp of the Funeral Mountains. The steep mountain front is cause by normal faulting. Rocks in the basin are dropping down relative to the mountain.	Figure 7. Wineglass valleys form where valley widening cannot keep pace with incision cause by rapid uplift. ( See D. Bains' panorama)

Figure 8.  Copper Canyon Turtleback--a dome of Precambrian rock with a curved fault surface. Photo by Gary Hayes ( Death Valley Field Trip Page.) The younger rock above the folded listric fault has been removed  by erosion.

Volcanic Activity

Thinning and fracturing of the crust also leads to decompression melting and volcanic activity.  Magma migrating through the fractured crust has added numerous small volcanic features to the landscape.   At the park's north end lies  a series of explosion craters called maars.  This cluster of pits and craters is known as the Ubehebe Volcanic Field.  The largest feature, Ubehebe Crater (2003, Don Bains), has a relief of 777 feet, from rim to pit floor, and a diameter of 5 miles.  Ubehebe in a Native American name meaning  "big basket in rock".  From sediment found beneath debris blasted from the crater geologists estimate the Ubehebe to be around 6,000 years old.  The crater was formed when magma intruding at depth super-heated groundwater and created a pressurized steam system that blasted through the overlying rock.  Unlike most volcanic features maars, produce very little lava or volcanic ejecta. However, cinder cones composed of basaltic ejecta are periodically encountered along faults in Death Valley.  One such cone is split cinder cone, which is offset by the fault over which it formed.

Ubehebee Crater

Ubehebe Crater & The Race Track: MUST-SEE SPOTS - For more funny movies, click here

Features formed by deposition

The Basin and Range is also know as the Great Basin because stream don't flow out.  Unlike the Colorado River that carries its sediment to the ocean, streams in the Basin and Range discharge into local basins.  This type of drainage system is referred to as an interior drainage.  Death Valley is surrounded by mountains and is so arid that water only escapes by evaporation. Streams are incapable of carrying sediment beyond the valley floor. Coarse gravelly and mud are deposited along the basin margins. Water evaporating from ephemeral lakes (playas) on the valley floor leaves behind a variety of salt deposits. The water is so alkali that it is poisonous, hence the term "badwater". Death Valley is the classic example of an arid basin with an interior drainage. Open any textbook on Physical Geology or Geomorphology and you'll find one or more of its features displayed on the pages.   Death Valley's arid basin contains classic examples of alluvial fans (images: 1, 2, 3, 4), bajadas, playas, and salt pans.  Short intense rain storms cut deep canyons into the rising mountains.  As these confined streams reach the basin floor they lose power, depositing their load in fan shaped bodies called alluvial fans.  Numerous discrete symmetrical fans dot the eastern flank of the valley in the vicinity of Badwater. These classic alluvial fans are undoubtedly the most photographed in North America.  On the western side, along the eastern front of the Panamint Range, large fans have coalesced forming a continuous apron of sediment called a bajada.  The asymmetrical distribution of fans and bajadas along the margins of Death Valley is caused by eastward tilting of the basin floor.  Water reaching the basin floor may form a temporary lake or playa but eventually evaporates leaving behind it's dissolved load.  Badwater basin fluctuates between a salt pan (2002, Don Bains) and a playa (2005, Don Bains) as it periodically fills and dries.

Figure 9.  Satellite image of Death Valley. The western margin is flanked by a wide continuous bajada.  Small symmetrical fans are hidden in the shadows of the Black Mountains along the east flank of the basin.  Evaporite deposits appear white. Badwater playa(-282) is the large solid white region.  Telescope Mt. (11,049 feet) is southwest of Badwater in the Panamint Range. Rollover to see generalized fault structure of the basin.   The valley is only 3 million years old and is filled with approximately two miles of sediment.

Landscapes created by erosion

Few features seen on the Colorado Plateau are found in Death Valley.  There are no flat topped mesas and buttes, no arches and fins, and no linear strike valleys and ridges.  Canyons are V-shaped or Y-shaped (e.g. wineglass canyons) and lack the alternating slopes, cliffs, and benches so characteristic of the Colorado Plateau.  There are several reasons for these differences, however the principle reason is the structure, integrity, and composition of the material being eroded.  Mountain streams are eroding highly folded and shattered rock. Imagine first carving through a layer cake (c.f. Colorado Plateau), and then carving through the same cake after its been dropped from a 2-story building (c.f. Death Valley). Your slices would show little resemblance. (c.f. Badwater, Mosaic Canyon, Armagosa Chaos)

Along the mountain front the principal process is deposition.  However, where new faults step towards the basin a shift in relative base level exposes older alluvium and lake deposits to erosion.  Erosion of poorly vegetated, easily eroded, mud-rich strata produces a highly dissected rounded landscape known as badlands topography.  You could see a hint of badlands topography developing in Bryce Canyon National Park where destruction of resistant layers exposed the soft underlying mudrocks. Badlands topography is much more prevalent in Death Valley where streams attack poorly cemented Pliocene and Quaternary deposits.  The best areas to view badlands in Death Valley are Zabrinski Point and the colorful Artists Drive.

Evaporite Minerals

Evaporite minerals in Death Valley include halite (rock salt), gypsum, anhydrite, calcite, a variety of borate minerals, such as colemanite an ulexite.  Ulexite, a borate mineral with unique optical properties is one of my favorite. The Death Valley region is one or the greatest sources of borax in the United States.  See Boron Minerals of Death Valley.

Pleistocene Lakes

Death Valley wasn't always so dry. Like most basins in the province, Death Valley was not glaciated, but experienced milder conditions during the ice age (Pleistocene Epoch).   Lower evaporation rates and increased precipitation resulted in the formation of a 100-mile long lake called Lake Manly.   Lakes like this, formed under milder conditions, are know as pluvial lakes.  The largest in the western U.S. was Lake Bonneville in Utah, which filled basins in and around Great Salt Lake.  Lake Bonneville was approximated the size of Lake Michigan. When it dried up, around 6000 years ago, it left behind the 159-square-mile Bonneville salt flats, famous for its speedway, where the highest land speeds are recorded.  There were approximately 140 pluvial lakes in the Basin and Range during the Pleistocene Epoch. Their existence is recorded in the salt deposits, as well as relict beach deposits and wave-cut benches called strandlines.  In Death Valley these ancient waterlines are imprinted on valley walls, and volcanic cones that formed islands in the lake.  One of the best locations to see strandlines left by Lake Manly is shoreline butte.  The elevation of the highest strandline is 285 feet, indicating that the lake had a maximum depth between 500-600 feet. The exact depth can't easily be determined because the basin floor is actively subsiding and filling with sediment.

Strange Features and Phenomena

Race Track Playa

Other Sites and References

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