Death Valley Ecosystems

Faults

Faulting is the one of the main reasons Death Valley exists. Movement along faults allow the mountains to rise and the valleys to sink. Death Valley is located in the southwestern portion of the Basin and Range geomorphic province. The Basin and Range province has a long and active geologic history, including faulting and regional tectonic movement. Fault-bounded uplifted ranges are separated by down-dropped sedimentary basins.

Most faulting that is presently occurring within Death Valley is strike-slip (transverse) with a component of normal movement (see Figure 1). With faulting comes the possibility of seismic activity, more commonly known as earthquakes. Most earthquakes that occur today are very small and cause no damage to structures or the ground surface. However, at some point in the future (no one knows how long into the future), the major fault systems in Death Valley are almost sure to create a significant seismic event.

Geologic Formations

Death Valley National Park is one of many units within the National Park service established because of its underlying geologic theme. Death Valley NP is renowned world-wide for its exposed, complex, unique tectonics and diverse geologic resources. Contained within its boundaries is a diverse rock record stretching throughout most of geologic time. From 1.8 billion-year-old metamorphic rocks exposed in the Black mountains, to recent playa sediments deposited in the valley basins, Death Valley possesses a superb geologic record. Paramount is the realization that Death Valley’s geology is an ongoing dynamic process. Wind, water, and plate tectonics are still hard at work, shaping the park on a day-to-day basis.

Weather and Climate

Death Valley is famous as the hottest and driest place in North America. Summer temperatures often top 120°F (49°C) in the shade with overnight lows dipping into the 90s°F (mid 30s°C.) Average rainfall is less than 2 inches (5cm), a fraction of what most deserts recieve. Occasional thunderstorms, especially in late summer, can cause flashfloods.

In contrast to the extremes of summertime, winter and spring are very pleasant. Winter daytime temperatures are mild in the low elevations, with cool nights that only occasionally reach freezing. Higher elevations are cooler than the low valley. Temperatures drop 3 to 5°F (2-3°C) with every thousand vertical feet (approx. 300m). Sunny skies are the norm in Death Valley, but winter storms and summer monsoons can bring cloud cover and rain. Wind is common in the desert, especially in the spring. Dust storms can suddenly blow up with approaching cold fronts.

Why is Death Valley's weather so extreme?

Why so Dry?

Winter storms moving inland from the Pacific Ocean must pass over mountain ranges to continue east. As the clouds rise up they cool and the moisture condenses to fall as rain or snow on the western side of the ranges. By the time the clouds reach the mountain's east side they no longer have as much available moisture, creating a dry "rainshadow". Four major mountain ranges lie between Death Valley and the ocean, each one adding to an increasingly drier rainshadow effect.

Why so Hot?

The depth and shape of Death Valley influence its summer temperatures. The valley is a long, narrow basin 282 feet (86 m) below sea level, yet is walled by high, steep mountain ranges. The clear, dry air and sparse plant cover allow sunlight to heat the desert surface. Heat radiates back from the rocks and soil, then becomes trapped in the valley's depths. Summer nights provide little relief as overnight lows may only dip into the 85°F to 95°F (30°C to 35°C) range. Heated air rises, yet is trapped by the high valley walls, is cooled and recycled back down to the valley floor. These pockets of descending air are only slightly cooler than the surrounding hot air. As they descend, they are compressed and heated even more by the low elevation air pressure. These moving masses of super heated air blow through the valley creating extreme high temperatures.

How extreme is Death Valley's climate?

Record Temperatures

The hottest air temperature ever recorded in Death Valley (Furnace Creek) was 134°F (57°C) on July 10, 1913. During the heat wave that peaked with that record, five consecutive days reached 129° F (54°C) or above. Death Valley held the record for the hottest place on earth until 1922.

Oddly enough, 1913 was also the year that saw Death Valley's coldest temperature. On January 8 the temperature dropped to 15°F (-10°C) at Furnace Creek.

Longest summers

The greatest number of consecutive days with a maximum temperature of 100° F or above was 154 days in the summer of 2001. The summer of 1996 had 40 days over 120° F, and 105 days over 110° F. The summer of 1917 had 43 consecutive days with a high temperature of 120° F or above.

Highest ground temperatures

The highest ground temperature recorded was 201° F at Furnace Creek on July 15, 1972. The maximum air temperature for that day was 128° F. Ground temperature on the valley floor is about 40% higher than the surrounding air temperature.

Dry as a bone

No rain was recorded in the years of 1929 and 1953. The driest stretch on record was only 0.64 inches (1.6cm) of rain over a 40-month period in 1931 to 1934.

Weather data was compiled from park and National Weather Service record summaries for the years 1911 through 2007 for Furnace Creek in Death Valley, California.

Springs and Seeps

Evolution Islands

Wetland and riparian areas have a unique scientific value. The Death Valley / Ash Meadows area is a classic example of a plant and animal laboratory in evolution. This fact is due to the relatively recent development of the desert climate and a unique geologic history where large marshes and lakes were relatively plentiful as recently as 15,000 years ago. This combination of events has had the unusual result of confining several aquatic species that were probably widespread at the start of the last Ice Age to remnant wetlands that have persisted for thousands of years.

The presence of the unique suite of pupfish in the Death Valley region is comparable to the presence of land tortoises and Darwin's finches on the Galapagos Islands. Both animal groups originally colonized their respective areas thousands of years ago and became isolated in separate habitats that possess different environmental conditions. Through time, natural selection and isolation transformed a limited number of ancestral lines into several unique varieties. The existence of nine pupfish species and subspecies in isolated wetlands along the Amargosa River is therefore akin to the 13 finch species and 15 tortoise subspecies on the isolated islands of the Galapagos archipelago. In each case, differences in species were aided by the separation of populations that could not cross inhospitable habitats.

Extremes on the Galapagos Islands have helped to shape the physical characteristics and tolerances of the tortoises on different islands and the same general process of natural selection has affected pupfish which inhabit wetlands along the Amargosa River. The fish have, for example, developed/retained an ability to live in water that is 2.5 times more saline than seawater. With regard to temperature, some pupfish are able to live for short periods in water temperatures equal to 107° Fahrenheit. Both of these adaptations are important in a desert environment where water saltiness and temperatures are significantly greater than other areas in the United States. Each type of pupfish has evolved to the extent that they are physically distinct and genetically different. Differences in breeding behavior have been documented for pupfish in habitats that are relatively close to one other but possess different environmental conditions. In a similar vein, genetic variation has also been found in different populations of speckled dace along the Amargosa River. This fact suggests that "each desert wetland community functions as an evolutionarily significant unit" (Sada et. al 1995).

Much of the genetic and physical variability in the pupfish has been attributed to different environmental conditions that exist in different wetlands (e.g. warm spring orifices vs. cool spring outflows, high salinity vs. low salinity areas) and differences in population size which are influenced by habitat size (small springs vs. large springs). This relationship suggests that pupfish evolution is highly dependent on the maintenance of natural habitats, and that human modifications to environments will alter the course of natural selection.

Regional loss and degradation of wetland and riparian resources increases the value of pristine habitats inside Death Valley National Park. California has lost a greater percentage of its wetland acreage than any other state with 91% of the original habitats being drained, filled, or manipulated. Nevada has lost 52% of its original wetlands, and only 0.3% of the state acreage is now classified as a wetland. Loss of riparian habitats in California, Arizona and New Mexico has been so extensive that they have been considered to be endangered ecosystems.

In short, the unique plants and animals that exist within the biological laboratory of Death Valley National Park offer significant scientific opportunities. At some future time, these species may hold the key to understanding how fast evolution takes place, as well as how plants and animals adapt physically and behaviorally to their immediate surroundings.

Salt Flats

The salt flats in Badwater Basin cover nearly 200 square miles, among the largest protected salt flats in the world.

Salt flats are too harsh for most plants and animals to survive, yet are quite fragile. Delicate crystals are easily crushed and the relatively thin upper crust of salt can break through to the mud layer below, leaving tire tracks and even footprints. For this reason, vehicles are prohibited off established roads in Death Valley.

What causes salt flats?

• Source of salts, usually from a large drainage system
• Enclosed basin that doesn't drain to the sea and wash away the salts
• Arid climate where evaporation exceeds precipitation, leaving behind just the salts and fine silt

Salt of the Earth

Sodium Chloride—better known as table salt—makes up the majority of salts on Badwater Basin. Other evaporative minerals found here include calcite, gypsum, and borax.

Intense Concentration

The source of Badwater’s salts is Death Valley’s drainage system of 9,000 square miles—an area larger than New Hampshire. Rain falling on distant peaks creates floods that rush ever lower. Along the way, minerals dissolve from rocks and join the flood. Here, at the lowest elevation, floods come to rest, forming temporary lakes. As the water evaporates, minerals concentrate until only the salts remain. After thousands of years, enough salts have washed in to produce layer upon layer of salt crust.

Crystal Power

The vast, surreal salt flats of Badwater Basin change constantly. Salt crystals expand, pushing the crust of salt into rough, chaotic forms. Newly formed crystals ooze between mudcracks, sketching strange patterns on the surface of the salt flat. Passing rainstorms wash off windblown dust and generate a fresh layer of blinding white salt.

Floods create temporary lakes that dissolve salts back into solution, starting the process all over again.

Lowest Places on Earth

Earth’s Lowest Elevations

• Dead Sea (Jordan/Israel) -1360 feet (-414 m)
• Lake Assal (Djibouti, Africa) -509 feet (-155 m)
• Turpan Pendi (China) -505 feet (-154 m)
• Qattara Depression (Egypt) -435 feet (-133 m)
• Vpadina Kaundy (Kazakstan) -433 ft (-132 m)
• Denakil (Ethiopia) -410 ft (-125 m)
• Laguna del Carbón (Argentina) -344 ft (-105 m)
• Death Valley (United States) -282 ft (-86 m)
• Vpadina Akchanaya (Turkmenistan) -266 ft (-81 m)
• Salton Sea (California) -227 ft (-69 m)
• Sebkhet Tah (Morroco) -180 ft (-55 m)
• Sabkhat Ghuzayyil (Libya) -154 ft (-47 m)
• Lago Enriquillo (Dominican Republic) -151 ft (-46 m)
• Salinas Chicas (Argentina) -131 ft (-40 m)
• Caspian Sea (Central Asia) -92 ft (-28 m)
• Lake Eyre (Australia) -49 ft (-15 m)

Rock Bottom

As the lowest point in North America, Death Valley belongs to a world-wide geographic rogues’ gallery, whose members share these defining features:

To have exposed land below sea level, an extremely dry climate is necessary. In wet climates, low places fill with water and overflow to the sea. A dry climate evaporates water, leaving behind salt flats or briny lakes.

Like most of these locations, Death Valley was not created by a river’s erosion. Movements in the earth’s crust have dropped it to such great depths.

Below Sea Level

Sea level is the average elevation of the world’s ocean surface and is the standard from which all other elevations are measured. Regardless of tides, “sea level” remains constant.

Devils Hole

The Devils Hole detached unit of Death Valley National Park is habitat for the only naturally occurring population of the endangered Devils Hole Pupfish (Cyprinodon diabolis). The 40 acre (16 ha) unit is a part of the Ash Meadows complex, an area of desert uplands and springfed oases designated a national wildlife refuge in 1984.

Ash Meadows

Ash Meadows is the discharge point for a groundwater system extending over a hundred miles to the northeast. Thirty seeps and springs bring to the surface "fossil" water which entered the groundwater system thousands of years ago. Ash Meadows is home to 26 species of endemic plants and animals, including three other endangered fish (two of them pupfish) and seven threatened plants.

Devils Hole Pupfish

Earlier pluvial (or wet) periods allowed colonization of present sites; subsequent xeric (or dry) conditions served to isolate the aquatic habitats, with the result that the inhabiting organisms have differentiated and evolved into the relict species found today. The Devils Hole pupfish have been isolated 10,000 to 20,000 years, longer than any other in the Death Valley system. Devils Hole itself is a water-filled cavern cut into the side of a hill. The cavern is over 500 feet (152 m) deep and the bottom has never been mapped. Devils Hole provides its resident pupfish with conditions of constant temperature (92oF, 33oC) and salinity, unlike the fluctuating environments of many other pupfish. Although pupfish have been found as deep as 66 feet (20 m), the fish forage and spawn exclusively on a shallow rock shelf near the surface, feeding on the algae and diatoms found there. The Devils Hole pupfish is considered an annual species, with the historic population fluctuating between 100 - 200 in winter and 300-500 in late summer. Research indicates that pupfish population numbers respond primarily to the amount of algae present on the shelf. The algal growth depends, in turn, on the amount of solar radiation the shelf receives and the concentration of nutrients in the water. Finally, recent evidence suggests that nutrient availability is highest when the cave is used by barn owls (Tyto alba) as a roosting/nesting site; the owls increase the pool nutrient levels by casting nutrient-rich pellets into the water.

Conservation Efforts

The history of conservation efforts for the Devils Hole pupfish is instructive. The Devils Hole unit was added to Death Valley National Monument by presidential proclamation in 1952. Ten years later the NPS installed a hydrograph in the Hole to monitor water levels. Subsequently, the Hole was fenced after two divers drowned in its water. In 1967 the Devils Hole pupfish was officially listed as an endangered species.

New Threats

That same year saw a farming corporation amass 12,000 acres (4,900 ha) in the Ash Meadows area; by 1968 the hydrograph had begun to register a decline as large capacity wells were drilled and pumped in Ash Meadows. The alarming water drop threatened to expose the critical spawning/feeding shelf and precipitated the formation of two groups to work for protection of Devils Hole: the Desert Fishes Council in the West, and the Desert Pupfish Task Force in Washington D.C. By 1970, drastic conservation efforts had been undertaken: refugia populations were established, and a floating artificial shelf, artificially lighted, was suspended in Devils Hole to substitute for the partially exposed natural rock shelf. The fish never used the artificial shelf. In August of 1971 a federal court issued an injunction to halt further pumping, that threatened to completely expose the natural shelf. Further litigation finally resulted in the landmark Supreme Court decision of 1976 (Cappaert vs. U.S.). It recognized the prior water right of Devils Hole vis-a-vis its designation as part of a national monument. The permanent injunction did not halt pumping, but limited it to a level which guaranteed sufficient water to inundate the natural rock shelf.

Recovery

In their Devils Hole pupfish recovery plan of 1980 the U.S. Fish and Wildlife Service designated as essential habitat about 21,000 acres where the groundwater most influenced the water level in the Hole. One of the identified goals of the recovery plan was to maintain the aquifer at such levels that the population fluctuates from 300 in winter to 700-900 in late summer. The water source for the Devils Hole pupfish was now adequately secured, but the remainder of Ash Meadows was as yet unprotected. A land development company bought the Ash Meadows land from the farm corporation in 1977, planning to subdivide the area into 30,000 residential lots. This new threat to the Ash Meadows region prompted California Senator Alan Cranston to introduce legislation in 1981 which would establish a Desert Pupfish National Wildlife Refuge. Furthermore, in 1982 the U.S. Fish and Wildlife Service emergency-listed as endangered two more of the fish species in Ash Meadows, thereby conferring protection to all three levels of pools in the area. Finally, in 1984 Ash Meadows National Wildlife Refuge was established by Congress. The Nature Conservancy bought the bulk of the land from the development company and resold it to the USFWS. By 1986 the USFWS had drafted a recovery plan for the entire Ash Meadows area, including Devils Hole.

A Mysterious Decline

Starting in the mid-1990s, the Devils Hole pupfish population began what was to become a severe decline. Studies have been undertaken to better understand energy flow in the system, water chemistry, pupfish genetics, organisms living the the water, and other factors. Although the decline’s cause has not yet been determined, knowledge of the Devils Hole ecosystem has been greatly extended. Efforts continue to save this species that has existed for ten thousand years.