Round Top is a mountain located on the

Sierra crest The Sierra Crest is a roughly generally north-to-south ridge, ridgeline that demarcates the broad west and narrow east slopes of the Sierra Nevada and that extends as far east as the Sierra's escarpment, topographic front (e.g., Diamond Mountain ...

Alpine County, California Alpine County is a county in the eastern part of the U.S. state of California located within the Sierra Nevada on the state border with Nevada. As of the 2020 census, the population was 1,204, making it California's least populous county. T ...

, United States. Its summit is the highest point in

Eldorado National Forest Eldorado National Forest is a U.S. National Forest located in the central Sierra Nevada mountain range, in eastern California. Geography Most of the forest (72.8%) lies in El Dorado County. In descending order of land area the others countie ...

and the

Mokelumne Wilderness The Mokelumne Wilderness is a federally designated wilderness area located east of Sacramento, California. It is within the boundaries of three national forests: Stanislaus, Eldorado and Toiyabe. First protected under the Wilderness Act of ...

. The mountain lies just south of

Carson Pass Carson Pass is a mountain pass on the crest of the central Sierra Nevada, in the Eldorado National Forest and Alpine County, eastern California. The pass is traversed by California State Route 88. It lies on the Great Basin Divide, with the W ...

. With of

prominence In topography, prominence or relative height (also referred to as autonomous height, and shoulder drop in US English, and drop in British English) measures the height of a mountain or hill's summit relative to the lowest contour line encircling ...

, Round Top is the 16th most prominent mountain in the

Sierra Nevada The Sierra Nevada ( ) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...

Geology

Round Top is the remnant of a

volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most oft ...

that formed in the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

epoch, which lasted from 23 million years ago to 5 million years ago. Most of the mountain's vertical height consists of an intrusive

volcanic plug A volcanic plug, also called a volcanic neck or lava neck, is a volcano, volcanic object created when magma hardens within a Volcanic vent, vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if risi ...

formed of

basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Ameri ...

. This intrusive structure formed under the volcano's surface as subsurface

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

gradually cooled and solidified. Approximately is exposed by the northern wall of Summit City canyon, which forms the south face of the mountain. A strong magnetic anomaly in the vicinity indicates that this plug further extends far below the canyon floor. The upper layers of the mountain are made up of

extrusive rock Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. In cont ...

s, which formed at the surface. A succession of lava flows form the bulk of these upper layers. Some solidified mudflows are also present. The rock that forms Round Top was more resistant to

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

than other strata of the

. Eventually, over a

geologic time scale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochro ...

, these other strata wore away, revealing the erosion-resistant remnants which make up the mountain that remains today. It has a flank

lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...

, called

Elephants Back Elephants Back is a mountain summit located in Alpine County, California, United States. Description This landmark of Hope Valley is set in the Mokelumne Wilderness of the Sierra Nevada mountain range. The summit is situated one mile south ...

Ecology

The north slope of Round Top is home to a number of tree species, most prominently

whitebark pine ''Pinus albicaulis'', known by the common names whitebark pine, white bark pine, white pine, pitch pine, scrub pine, and creeping pine, is a conifer tree native to the mountains of the western United States and Canada, specifically subalpine ...

, western white pine, and

lodgepole pine ''Pinus contorta'', with the common names lodgepole pine and shore pine, and also known as twisted pine, and contorta pine, is a common tree in western North America. It is common near the ocean shore and in dry montane forests to the subalpin ...

. The summit of the mountain rises above the

tree line The tree line is the edge of a habitat at which trees are capable of growing and beyond which they are not. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually low ...

. Western white pine and lodgepole pine grow up to about . The whitebark pine survives in the form of short, stubby

krummholz ''Krummholz'' (, "crooked, bent, twisted" and ''Holz'', "wood") — also called ''knieholz'' ("knee timber") — is a type of stunted, deformed vegetation encountered in the subarctic and subalpine tree line landscapes, shaped by continual e ...

to as high as . A specimen of the Lake Tahoe lupine (''Lupinus meionanthus'') has been identified at the summit of Round Top.

History

In 1872, prospectors began exploring the Summit City Creek canyon immediately south of Round Top, ultimately filing more than 30 mining claims in the area. At some point before 1879, George Davidson of the

United States Coast and Geodetic Survey The United States Coast and Geodetic Survey ( USC&GS; known as the Survey of the Coast from 1807 to 1836, and as the United States Coast Survey from 1836 until 1878) was the first scientific agency of the Federal government of the United State ...

established a geodetic station on the summit of the mountain, as part of a chain of such stations atop peaks along the Sierra crest.

Climbing

Round Top is listed on the

Sierra Peaks Section The Sierra Peaks Section (SPS) is a mountaineering society within the Angeles Chapter of the Sierra Club that serves to provide mountaineering activities for Sierra Club members in the Sierra Nevada (U.S.), Sierra Nevada, and to honor mountaineers ...

peak list. Reaching the summit requires a class 3 ascent. The circumstances of the first ascent are unknown.

References

{{coord, 38.66352, -120.00129, format=dms, type:mountain_region:US-CA, display=title Sierra Nevada (United States) Eldorado National Forest Mountains of Alpine County, California Volcanoes of California