Great Basin National Park

Geology

Great Basin National Park has a rich geologic history

Rivers and Streams
Ten permanent streams originate in Great Basin National Park between 6,200 and 11,000 ft. (1,890 and 3,353 m) elevation and are fed by numerous springs along their courses. The streams are first and second order headwater streams with an average length of 8 km (5 mi) within the park.

Great Basin’s Streams
Six streams (Strawberry, Mill, Lehman, Baker, Snake, and South Fork Big Wash) flow eastward into Snake Valley and the Bonneville Basin. The other four streams (Shingle, Pine, Ridge, and Williams) flow westward into Spring Valley and were originally fishless. Outside park boundaries the majority of these streams are used for irrigation; some water evaporates or percolates into the alluvium before reaching the valley bottom. None of the water flows outside of the Great Basin hydrologic basin.

Stream Life
The variety of habitat types in Snake Range streams supports a diverse spectrum of aquatic insects and invertebrates. Over 100 species of aquatic insects live in the streams. Mayflies, caddisflies, stoneflies, as well as scuds, leeches, and snails are all prominent food sources for resident fish. Bonneville cutthroat trout and three other native fish species are found in park streams, along with some nonnative species.

Seasonal Flow
The amount of water in the creeks varies widely. Baker Creek may only have 1.5 cubic feet per second (cfs) flowing in the winter, but during spring runoff it can exceed 200 cfs. In order to measure the streamflow, Baker and Lehman Creeks have been instrumented with United States Geological Survey (USGS) stream gauges for over 13 years.

Research
Stream gauges were installed by the USGS in 2002 for two years on Strawberry, Snake, South Fork Big Wash, Shingle, Decathon, and Williams Creeks as part of a study to determine the susceptibility of park water resources to groundwater pumping in adjacent valleys (Elliott et al 2006). Gauges are currently being monitored on Lehman Creek by the USGS; and Baker, Rowland, and Snake at the park boundary by park staff. Some of the data can be accessed at: http://waterdata.usgs.gov/nv/nwis.

A number of studies are underway on the streams in the park. These include annual monitoring of fish populations, a baseline water quality inventory, maintaining and operating stream gauges, and periodically monitoring of macroinvertebrates, physical habitat, and riparian vegetation.

Faults
Nevada is one of the most seismically active states in the country, ranking third after California and Alaska. To blame are the state’s many faults, found at the base of almost every mountain range. The basin and range topography of the Great Basin is caused by movement along these faults. As these mountain ranges continue to grow through fault-block activity, earthquakes continue to occur.

What is a Fault?
A fault is simply a fracture in the earth’s crust. Movement along faults displace the rock layers on either side. The mountains in much of the Great Basin are large blocks of rock that have been uplifted and tilted by normal activity along fault lines. The basins between the mountains, on the opposite sides of the faults, have slipped downward, and have been filled in and leveled by erosion of the mountains above. Geologists refer to these landforms as “fault-block mountains.”

Earthquake Activity
Most earthquake activity occurs along the eastern Sierra Nevada mountains, on the Nevada’s western border. The most powerful earthquake recorded in the state was a 7.6 magnitude quake that occured near Winnemucca in 1915.

While earthquakes don’t occur at any regular interval, historically the frequency of an earthquake of magnitude 6 or higher has been one every 10 years, and for magnitude 7 or higher, one every 27 years.

Cave / Karst Systems
Great Basin National Park contains over 40 known caves, filled with unique features. Some caves contain unique formations such as folia, bulbous stalactites, anthrodites, and shields. Some caves contain features that suggest that deep-seated, hydrothermal waters influenced the caves’ development. The park has high-elevation vertical shafts and horizontal solution caves that have formed along fracture planes.

Please Note: The only caves in the park open to the public are Lehman Caves, and eight permitted wild caves. All other caves remain closed to protect their fragile ecosystems.

Cave Systems
Four distinctive groups of caves exist in the park. These groups are Lehman Hill Caves, Baker Creek Caves, Snake Creek Caves, and Alpine Caves. Many of the caves within these groups may have formed together either hydrologically and/or structurally.

Lehman Hill Caves
Lehman Caves, Little Muddy Cave, Lehman Annex Cave, and Root Cave make up the Lehman Hill Cave System. The cave passages’ proximity and similar passage orientation supports that these caves may have formed from a single evolving drainage network.

Lehman Annex Cave is the highest in elevation at 7,300 ft. Because of its high elevation, it is thought to have been the first cave to form. Lehman Cave and Root Cave occur at around 7,000 ft. These two caves probably formed around the same period of time. Little Muddy Cave is at an elevation of 6,800 ft. This cave was discovered because of its spring-like appearance. It may have served as a spring for the system at some point in time. A nearby active spring may be today’s representative of the watercourse that formed Lehman Hill Cave System. The spring is buried in glacial alluvium and shows no external signs of being connected with a karst system.

Baker Creek Caves
In 1958, Arthur Lange investigated the caves of the Baker Creek area for the Western Speleological Institute and concluded that there was once only one system that was cut through the Baker Creek area (Bridgemon 1964). Ice, Crevasse, and Wheelers Deep Caves have been physically connected through cave exploration. Model, Systems Key, and Dynamite Caves have been shown to be connected to Ice-Crevasse-Wheeler Deep hydrologically.

Snake Creek Caves
The Snake Creek cave system includes Snake Creek Cave, Indian Burial Cave, and Fox Skull Cave.

Snake Creek Cave is the most popular wild cave in Great Basin National Park. The cave is known for its spectacular aragonite anthrodite and frostwork formations. Signatures from Morrison and Roland in 1886 show a long history of the cave’s visitation. The Snake Creek Cave entrance is at an elevation of 6700 ft, and the cave is approximately 1700 ft long.

Alpine Caves
Alpine caves are caves that occur at high elevation, typically above 9,000ft. Most of the park’s alpine caves can also be considered fracture caves since all initially formed along fracture planes.

High Pit is the highest solution cave found in the park and perhaps the entire state, at an elevation of 11,200 ft. The interesting features of this cave are its high elevation location and the nèvè (compacted, old snow) in its interior. The bottom of High Pit is plugged with snow.

Long Cold Cave is located at an elevation of about 10,000 ft. The cave is the deepest cave in the park (perhaps in Nevada) at a depth of 480 ft.

Lehman Caves Geology
Water working slowly over the ages is the sculptor of Lehman Caves. The beginning of Lehman Caves can be traced back to approximately 600 million years ago, in the early Cambrian period. Much of what is now Nevada and western Utah was covered by a warm, shallow, inland sea. During this time, many thick layers of sediment accumulated on the sea bottom. Some of the layers were composed of silt, some were sand, and still others were made up of a limy substance that originated from decomposed bodies of minute shell creatures.

One of these limy layers was to become the marble in which Lehman Caves formed. This limy layer was compacted greatly by the weight of latter sediments deposited upon it. Under this pressure, the limy layer slowly turned to limestone rock. Later, as pressure and heat increased, the limestone turned to a low-grade marble. Later, great forces under the earth’s crust caused the layers of rock to buckle. This mountain range (the buckle) rose gradually until its peaks were thousands of feet above the valley floor. The rock layers cracked and fractured from the stresses of the uplift. In the future, the pattern of these fractures would help determine the floor plan of the cave.

Acidic ground water came from melting snow and rain. Pure water could not dissolve marble. This water absorbed carbon dioxide from the air and decaying vegetation in the soil, which generated carbonic acid. This weak acid dissolved out cavities in the marble bedrock. Eventually, the water level dropped, leaving air-filled passageways ready for the next stage of cave development.

Seeping water continues to enter the cave at a slow rate. The weak acid dissolves some of the bedrock above the cave and redeposits the mineral (calcite) on the floors, ceilings, and walls of Lehman Caves. Many of the beautiful formations in Lehman Caves are still growing, and are very fragile.

Mountains
The “Great Basin” that Great Basin National Park is named after extends from the Sierra Nevada Range in California to the Wasatch Range in Utah, and from southern Oregon to southern Nevada. This is an area where no water drains to an ocean, but drains inward. As big as it is, the Great Basin is only part of an even larger region called the Basin and Range province that extends down into Mexico. The landscape around Great Basin National Park is a good example of what is found throughout the Basin and Range province – long mountain ranges separated by equally long, flat valleys.

Great Basin National Park encompasses most of the South Snake Range. The bulk of the rocks exposed in this range are formed of sediments like sand, mud and limey ooze (silt and clay particles mixed with calcium carbonate) that were laid down on the bottom of a shallow sea during the late Precambrian and Cambrian (around 560 million years ago).

The rocks in the park were further changed during a mountain-building event that occurred around 200 million years ago during the Mesozoic Era. This event, the Sevier Orogeny, pushed layers of rock on top of each other, doubling the thickness of the crust. The layers at the bottom of the stack were metamorphosed slightly – sandstone changed gradually into quartzite, limestone to low-grade marble. Magma rose from deep within the Earth and pushed its way up into these layers. It did not come to the surface, however. Staying underground, it cooled to become granite. Where this hot magma was intruded, the surrounding rock was metamorphosed slightly more.

After all of this activity, the region still did not resemble the present landscape. The modern basins and ranges began to appear only within the last 30 million years or so, during the Cenozoic Era, when the Earth’s crust in this area began to stretch in an east-west direction. Bedrock nearest the surface reacted to the crustal stretching by breaking into immense blocks several miles wide, tens of miles long, and thousands of feet thick. Many of these blocks fractured and the pieces tilted and spread out like a row of odd-sized books sliding out of place on a shelf. The remnants of these broken blocks lie beneath the sediment in the basins. Other blocks remained relatively intact and now form the mountain ranges. Because stretching is in an east-west direction, these ranges line up in a north-south direction. The South Snake Range was to see even more change. The younger unmetamorphosed layers of rock on top of the range slid off of the older metamorphosed rocks in a southeasterly direction, on a very low-angle fault line called a decollement. This event makes the South Snake Range a metamorphic core complex. The end of the Cenozoic Era witnessed more granitic intrusions into the park, as well as colder climates that further shaped the landscape.

Alpine glaciers, or cirque glaciers, were present here in the park in several locations along its spine during the Ice Ages. These glaciers carved the peaks to form the cirques like the one underneath Wheeler Peak. Other glacial remnants include terminal and lateral moraines, rocky ridges created at the ice’s edge as it pushed its way down the mountain slopes. However, these glaciers did not extend down to the floors of the valleys. Water was collecting in the basins, forming lakes of tremendous size. Lake Bonneville was one of the largest, growing to about the size of today’s Lake Michigan. The lakes began to disappear as the last ice age came to a close, but left behind small remnants like the Great Salt Lake and Sevier Lake.

Sevier Lake today is a playa lake, one that collects water in colder and wetter seasons, but dries up in warmer seasons. The evaporating water leaves behind vast stretches of salt flats. Erosion strips down the mountains, and carries sediments down to the valleys creating alluvial fans. These spread out from the canyons down to the valley floors and along with playa lakes, are classic geologic features of basin and range topography. Eventually the sediments are carried to the floor of the valleys, where they have accumulated in layers thousands of feet thick.

The crust beneath the Basin and Range is still stretching today. Faults are active, mountains are pushing upwards, and basins are widening and filling with debris washed down from the high country. This landscape, which appears so everlasting, is actually in the midst of a geologic revolution, played out over millions of years. As the crust continues to stretch, the North American Plate will eventually be divided into two pieces, and a new ocean will form in between them. A future visit to Great Basin National Park might entail an underwater excursion in scuba gear.

Glaciers / Glacial Features
Great Basin National Park is home to the only glacier in Nevada, and one of the southernmost glaciers in the United States. The Wheeler Peak Glacier sits at the base of Wheeler Peak, in a protected cirque around 11,500 feet in elevation. The glacier measures 300 feet long and 400 feet wide. Exact depth is unknown.

What Is a Glacier?
A glacier is a body of ice that lasts from year to year and that flows under its own weight. Glacial ice is made of crushed and recrystallized snowflakes. If the yearly snowfall is greater than yearly melting and evaporation, a glacier will grow. If melting is greater than snowfall, a glacier will shrink. A crevice that appears each summer near the head of the glacier indicates that the ice is moving.

There are two types of glaciers. Contintental ice sheets cover large areas with ice. Alpine glaciers, like the Wheeler Peak Glacier, are smaller, and found in mountainous terrian.

A Different Climate
The glacier is a remnant from the past, telling of a much different climate in a region that is now a desert. The Pleistocene (approx 3 million to 10,000 years ago) was a time of advancing glaciers alternating with warm, dry inter-glacial periods. Continental ice sheets lay to the north of the Great Basin region. Alpine glaciers sculpted some of the mountain ranges within the Great Basin, such as the South Snake Range in Great Basin National Park.

During the last glacial period, glaciers moved down to as low as 9,200 feet. The climate was an average 8 degrees (F) cooler than today. But climate changes that began with the Holocene period (10,000 years ago) rapidly warmed the region, melting the continental glaciers to the north, and the individual alpine glaciers within the region. The Wheeler Peak Glacier is the last alpine glacier to survive. With continued warming predicted, it is likely the glacier will disappear in as little as 20 years.

Ice Field or Rock Glacier?
The small glacier below Wheeler Peak has been incorrectly called an ice field. According to definition, an ice field is a vast body of ice, the union of several alpine glaciers. Ice fields are found today in Alaska and British Columbia.

It has correctly been referred to as a rock glacier, however. A rock glacier is a lobe of angular boulders and cobbles that resembles an alpine glacier in outline and in its slow downslope movement. They are found in mountain ranges throughout the world. Inside a rock glacier, ice fills the spaces between the blocks. By freezing, thawing, and sagging, the ice works with gravity to provide the force that moves the rock glacier.

Viewed from the cliffs above, arc shaped ridges are visible on the surface of the Wheeler Peak Glacier. These ridges are curved because the blocks near the midline of the rock glacier are creeping faster than those on either side.

Visiting the Glacier
The Wheeler Peak Glacier can be seen from several locations in the park.

The Wheeler Peak Overlook on the Wheeler Peak Scenic Drive is the only vantage point from the road. The glacier is seen at the bottom of the sheer rock face of Wheeler Peak.

The Bristlecone/Glacier Trail (4.6 miles roundtrip) will take you to the foot of the glacier. The trailhead for this hike is located at the end of the Wheeler Peak Scenic Drive. The trail begins at an elevation of 9,800 feet and climbs another 1,100 feet. Use caution around the toe of the glacier, as the boulders may not be stable, and small rockslides are common from the cliffs above.

see original article here: http://www.ohranger.com/great-basin/geology

Native American History

Home of the Western Shoshone, Goshute, Ute, Paiute, and Washoe

The tribal peoples now living in the Great Basin are descendents of the people who have been in the region for several hundred to several thousand years. When early explorers first entered the Great Basin, they encountered many different groups. And although there were several distinct tribes speaking various (but closely related) languages, the basic lifestyle was similar across the region.

The native people of the Great Basin knew the land intimately and understood the natural cycles. Small family groups hunted and gathered, patterning their lives to take advantage of the diverse and abundant resources. The land provided all their nutritional needs as well as materials for clothing and shelter. They hunted small and large animals, such as jackrabbits, antelope, and waterfowl; gathered pine nuts and berries; and dug roots and tubers. Enough food was harvested every summer and fall to carry them through the winters. Where the geography and climate allowed it, some also fished and farmed small plots. These were resilient, flexible, and adaptable people.

Explorers and settlers who encountered these tribes focused on their lack of material goods and labeled them as destitute, primitive, and savage. But the native people had lived off the land successfully for hundreds, even thousands, of years. Material goods would hinder their nomadic lifestyle, and remaining in one location would not allow them to take advantage of the seasonal cycles. Their lifestyle allowed them to survive in a harsh desert environment that pioneers thought of as inhospitable. The native people were craftsmen, weaving beauty into their baskets and painting their pottery. They made jewelry and told stories. They had families and religion. These were not the traits of destitute people barely scraping by, but of successful people with a rich culture.

Several distinct tribes have historically occupied the Great Basin; the modern descendents of these people are still here today. They are the Western Shoshone (a sub-group of the Shoshone), the Goshute, the Ute, the Paiute (often divided into Northern, Southern, and Owens Valley), and the Washoe.

With the exception of the Washoe, all the Great Basin tribes are Numic speaking, which means that their languages all belong to the Numic language group. They are not the same language, but are closely related. The Washoe language belongs to the Hokan family, which also includes the languages of several Californian and Southwestern tribes. Anthropologists use language to judge the relation of one people to another. Generally, the more closely related two languages are, the more closely related the people who speak them.

see original article here: https://www.nps.gov/grba/learn/historyculture/historic-tribes-of-the-great-basin.htm

Park History

How Great Basin became a National Park

The story of the Great Basin is not just one of geology and landforms, but also of people. This region has been home to American Indians for thousands of years. In more recent times, farmers, ranchers, Mormons, and sheepherders all called the Great Basin home.

Within Great Basin National Park, a representive piece of this massive region, stories of people and of places abound. Humans have left their mark, from the Fremont Indians, to the first explorer of Lehman Caves, Absalom Lehman, to the mining camps that once dotted the South Snake Range. Remnants of these times are invaluable links to the past, as worthy of preservation as much as any of the park’s natural resources.

see original article here: https://www.nps.gov/grba/learn/historyculture/index.htm

Attractions

The best things to do in Great Basin National Park

Lehman Caves. #1 of 13 things to do in Great Basin National Park. …
Lehman Caves Visitor Center. #2 of 5 things to do in Baker. …
Baker Creek Loop Trail. #3 of 5 things to do in Baker. …
Alpine Lakes Loop. #4 of 13 things to do in Great Basin National Park. …
Teresa Lake. …
Baker Lake Trail. …
Baker Archaeological Site.

Vegetation

Despite the dry conditions, there are over 800 different plant species in Great Basin National Park

The Great Basin is a desert, averaging less than 10 inches of rain a year. It is a cold desert, and because of its high elevation, it receives most of its moisture in winter snows. Despite these dry conditions there are over 800 different plant species in the park and South Snake Range, of these 13 are considered sensitive species. The way many of these plant species are able to survive in this environment is through specialized adaptations or by living in the cooler, wetter mountain ranges.

Dealing With Little Water
Many flowering plants will only grow and produce seeds during a year when there is enough water. These seeds will be dormant until the next season with enough moisture, which may be years from the time they were produced.

Other adaptations help keep plants from losing their water. The Sagebrush, a very common resident of the Great Basin, is well adapted to the area. The Big Sagebrush root system can extend as much as 90 feet in circumference. This adaptation allows the plant to catch as much water as possible when the rains do come. The hairy leaves of sagebrush work as a windbreak to slow down evaporation from leaves. Other methods of water loss prevention are waxy leaves and succulence. The waxy coat acts as a barrier to evaporation by the wind. Succulence allows plants to hold water for the drier times. Greenleaf manzanita is an example of a plant with a waxy coat and prickly pear cactus is a succulent.

Plants exchange gases, including water, through their leaves by a process called transpiration. Plants in this area can not afford to lose much water through evapotranspiration (the process by which plants release oxygen and sometimes water) and have developed modified leaves. Mormon tea or joint fir possesses modified leaves. The leaves are very small and are not the primary area for photosynthesis. The chlorophyll filled stems carry out the primary photosynthesis.

Dealing With Salt
In other places the soils of the Great Basin contain high amounts of salt and only plants with special adaptations such as saltbush and iodinebrush can survive. Four-winged Salt bush excretes salt through its leaves this process prevents build-up of lethal salts in the plant. The plants on the alkaline flats have a high internal concentration of salt and are able to extract water other plants can not.

Importance of Adaptations
The plants in the Great Basin have developed some ingenious methods of dealing with the dry desert conditions. Their adaptations have allowed plants to live in harsh environments, providing a variety of habitats for animals.

see original article here: https://www.nps.gov/grba/learn/nature/plants.htm

Animal Life

The diversity of habitats in Great Basin National Park gives rise to a wide variety of animal life.

The diversity of habitats in Great Basin National Park gives rise to a wide variety of animal life. From sagebrush steppe to alpine areas, from caves to creeks, many species thrive.
Mammal Species (other than bats) in Great Basin National Park of Special Concern:

Water Shrew (Sorex Palustris)
Yellow-bellied Marmot (Marmota flaviventris)
Beaver (Castor canadensis)
Sagebrush Vole (Lagurus curtatus)
Porcupine (Erethizon dorsature)
Bighorn Sheep (Ovis canadensis)
Pygmy Rabbit (Sylvilagus idahoensis)
Ringtail Cat (Bassariscus astutus)

see original article here: https://www.nps.gov/grba/learn/nature/animals.htm

Hiking Trails

The best hiking trails in Great Basin National Park

Great Basin National Park offers over 60 miles of developed hiking trails.

Day hikers are asked to sign in at trailhead registers. Permits are not required for backcountry camping, but registration is free and strongly encouraged. Registering provides rescuers with critical information in case of an emergency. Stop at a visitor center or call (775) 234-7510 for current information on trail conditions and routes.

Access
The hiking season at Great Basin National Park is typically limited to the months of June through September because many trails are at elevations of 9,000 feet or more. The Wheeler Peak Scenic Drive is not plowed and may not open until mid-June, weather depending. Gravel roads that lead to the remote southern section of the park are impassable until late spring. Four-wheel drive is required on some of these roads, especially when wet. Inquire at the visitor center or call (775) 234-7510 for more information on current road conditions.

Trails
If trails are provided, stay on them. Alpine communities are especially fragile and easily damaged. Taking shortcuts creates a complex web of trails and causes erosion. When traveling cross country, avoid damaging vegetation by staying on durable surfaces such as rock or mineral soil.

Map reading skills are essential to any off-trail travel in the park. Backpackers should be prepared to hike cross-country on hard-to-follow routes, or to follow drainages, ridges and other natural features.

Pets
Pets are not allowed in the backcountry or on trails, with one exception. Leashed pets are allowed on the Lexington Arch Trail, a day use only area.

Bicycles
Bicycles are prohibited on all trails.

Firearms
In accordance with recent changes in federal law, under certain circumstances the possession of firearms is allowed in Great Basin National Park. Please visit the firearms webpage for more information.

Smoking
Persons who wish to smoke while hiking in the backcountry must stop and remain in one location until they have extinguished their smoking material. All smoking material must be packed out and disposed of in an appropriate trash receptacle.

Water
Hikers and backpackers are advised to carry ample water on any trip. Water sources in the backcountry are highly variable from year to year and season to season. Generally, late spring is the time of most abundant water. By late summer, streams and springs can be dry. All surface water should be treated by boiling or filtering to kill bacteria before drinking.

Staying hydrated is important when hiking in desert regions. Bring plenty of water and drink it!

Human Waste Disposal
In backcountry and other undeveloped areas, the disposal of human body waste is prohibited within 100 feet of any water source or developed trail. Human waste should be buried in a hole 6-8 inches deep in mineral soil or packed out. Toilet paper must be packed out and disposed of in park restroom facilities.

Camping
Backcountry camping is not permitted within 1/4 mile of any developed site (i.e. road, building, campground, etc.), within the Wheeler Peak or Lexington Arch Day Use Areas, or in Bristlecone pine groves. Camping is prohibited in all parking areas, at trailheads, and on or along all other roads.

Campsites must be a minimum of 100 feet away from a flowing stream, spring, lake or other natural body of open water and at least 500 feet from any obvious archeological site (such as historic mine sites, cabins, rock shelters, pictograph sites). Camp on mineral soil if possible and avoid camping in the treeless alpine zone. The maximum continuous stay at any campsite is 14 days.

Group Size
Group size is limited to 15 persons and/or 6 pack animals in the backcountry. Larger groups must split into smaller groups within these limits and must camp at least 1/2 mile apart. Larger groups may request an exception to these limits from the Superintendent under the terms of a Special Use Permit.

Fires
Campfires are not allowed above 10,000 feet. Backcountry users may only use propane stoves above this elevation. Note that both Baker Lake and Johnson Lake, popular backcountry destinations, are above 10,000 feet and campfires are prohibited.

Below 10,000 feet, only dead and down wood (already on the ground) may be collected. Bristlecone pine wood may not be burned, even if dead and down. If conditions warrant, fires may be prohibited in the backcountry.

Fires may only be constructed upon and in areas of bare soil with a diameter of at least 10 feet or in a shallow snow pit clear of vegetation for a diameter of at least 10 feet in order to prevent escape and damage to resources. Metal fire pans or fire blankets may also be used in such areas for additional protection. Clearing of vegetation is prohibited. Fires may not exceed two feet in diameter and must be attended at all times.

Upon departure all fires must be rendered completely out and cold by dousing with water and all ashes must be widely scattered. Construction of stone fire rings is prohibited.

Pack Animals
Horses, llamas, and mules are allowed on a few backcountry trails as pack animals. Scatter manure piles at trailheads and at backcountry campsites. Remember to picket, hobble, or graze animals at least 100 yards from any water source. All packed feed must be certified weed-free.

Hazards
Be aware of other hazards that exist when hiking in the backcountry such as hypothermia, dehydration, altitude sickness and sun exposure. Prepare appropriately for these and other situations.

Abandoned mines are common in the backcountry. They can be extremely dangerous. Shafts and tunnels are unstable; do not enter them.

Weather
Elevations in the park range from 6,200 to 13,063 feet, which leads to highly variable weather conditions year round. At elevations of 10,000 feet and higher, snow and/or electrical storms can be life-threatening, and can occur any month of the year. Be prepared for changing conditions.

see original article here: https://www.nps.gov/grba/planyourvisit/guidelines-for-backcountry-use.htm