Little Jack is a mountain summit in the
North Cascades
The North Cascades are a section of the Cascade Range of western North America. They span the border between the Provinces and territories of Canada, Canadian province of British Columbia and the U.S. state of Washington (state), Washington and ...
of
Washington
Washington most commonly refers to:
* George Washington (1732–1799), the first president of the United States
* Washington (state), a state in the Pacific Northwest of the United States
* Washington, D.C., the capital of the United States
** A ...
, United States. It is located within the
Pasayten Wilderness. It is situated one mile south of its namesake
Jack Mountain, west of
Crater Mountain, and east of
Ross Lake. Like many North Cascade peaks, Little Jack is more notable for its large, steep rise above local
terrain
Terrain (), alternatively relief or topographical relief, is the dimension and shape of a given surface of land. In physical geography, terrain is the lay of the land. This is usually expressed in terms of the elevation, slope, and orientati ...
than for its absolute elevation. In the early 1900s, the Forest Service built the Little Jack Trail for the purpose of grazing pack animals on the meadows of Little Jack Mountain.
[Geology of the North Cascades: A Mountain Mosaic. by Rowland W. Tabor, Ralph Albert Haugerudme. The Mountainers publisher. 1999] The name "Jack" refers to Jack Rowley, a gold prospector in the area during the late 1800s, who was credited with finding gold at Ruby Creek.
Climate
Little Jack is located in the
marine west coast
An oceanic climate, also known as a marine climate or maritime climate, is the temperate climate sub-type in Köppen classification represented as ''Cfb'', typical of west coasts in higher middle latitudes of continents, generally featuring co ...
climate zone of western North America.
Weather front
A weather front is a boundary separating air masses for which several characteristics differ, such as air density, wind, temperature, and humidity. Disturbed and unstable weather due to these differences often arises along the boundary. For ins ...
s originating in the Pacific Ocean travel east toward the Cascade Mountains. As fronts approach the
North Cascades
The North Cascades are a section of the Cascade Range of western North America. They span the border between the Provinces and territories of Canada, Canadian province of British Columbia and the U.S. state of Washington (state), Washington and ...
, they are forced upward by the peaks of the Cascade Range (
orographic lift
Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and cr ...
), causing them to drop their moisture in the form of rain or snow onto the Cascades. As a result, the west side of the North Cascades experiences high precipitation, especially during the winter months in the form of snowfall.
Because of
maritime influence, snow tends to be wet and heavy, resulting in high
avalanche
An avalanche is a rapid flow of snow down a Grade (slope), slope, such as a hill or mountain. Avalanches can be triggered spontaneously, by factors such as increased precipitation or snowpack weakening, or by external means such as humans, othe ...
danger.
During winter months, weather is usually cloudy, but due to high pressure systems over the Pacific Ocean that intensify during summer months, there is often little or no cloud cover during the summer.
[ Beckey, p. 16] Precipitation
runoff from the mountain drains into the
Skagit River
The Skagit River ( ) is a river in southwestern British Columbia in Canada and northwestern Washington (state), Washington in the United States, approximately 150 mi (240 km) long. The river and its tributaries drain an area of 1.7&nbs ...
.
Geology
The North Cascades features some of the most rugged topography in the
Cascade Range
The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington (state), Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as m ...
with craggy peaks, ridges, and deep
glacial valley
U-shaped valleys, also called trough valleys or glacial troughs, are formed by the process of glaciation. They are characteristic of mountain glaciation in particular. They have a characteristic U shape in cross-section, with steep, straight s ...
s. The history of the formation of the Cascade Mountains dates back millions of years ago to the late
Eocene
The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
Epoch.
With the
North American Plate overriding the
Pacific Plate, episodes of
volcanic igneous activity persisted.
[ In addition, small fragments of the ]oceanic
Oceanic may refer to:
*Of or relating to the ocean
*Of or relating to Oceania
**Oceanic climate
**Oceanic languages
**Oceanic person or people, also called "Pacific Islander(s)"
Places
* Oceanic, British Columbia, a settlement on Smith Island, ...
and continental lithosphere
A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time sc ...
called terrane
In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its d ...
s created the North Cascades
The North Cascades are a section of the Cascade Range of western North America. They span the border between the Provinces and territories of Canada, Canadian province of British Columbia and the U.S. state of Washington (state), Washington and ...
about 50 million years ago.[ Little Jack Mountain is part of the ''Little Jack terrane''. Outcrops of ]granite
Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...
and fine-grained mica schist can be found on the top of Little Jack Mountain.Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
period dating back over two million years ago, glaciation advancing and retreating repeatedly scoured the landscape leaving deposits of rock debris.[ The U-shaped cross section of the river valleys is a result of recent glaciation. Uplift and faulting in combination with glaciation have been the dominant processes which have created the tall peaks and deep valleys of the North Cascades area.
]
Gallery
See also
* Geography of the North Cascades
The geography of the North Cascades describes a range of rugged mountains in British Columbia, Canada and Washington, United States. In Canada, the range is officially named the Cascade Mountains but is commonly referred to as the Canadian Cascad ...
References
{{reflist
Mountains of Whatcom County, Washington
Two-thousanders of the United States
North Cascades of Washington (state)