Formation of the Range of Light

The Sierra still retains the awesome splendor that Bierstadt encountered. We will look at Fly Fishing the Sierra from a Naturalist perspective. Not only will you appreciate the fly fishing opportunities but will get an appreciation for your surroundings, how they came to be, and where they might transform in the future. The Sierra Nevada has been an inspiration to many. A mountain range that John Muir referred to as the "Range of Light".

 

Most likely this was the place where you were introduced to fishing as a child.

 

    Explored Glacial Lakes

 

   Fished Clear Creeks

 

  Encountered Mountain Meadows

Hiking into areas still devoid of people. Awesome vistas.

 

The Sierra Nevada that we see today is a result of many processes that have occurred over millions of years.  This blog article will cover:

Plate Tectonics
Geology
Volcanic Activity
Glaciation
Climate Change
Flora Diversity
Human Impacts

 

Plate Tectonics

 

We start with an introduction to plate tectonics. Plate Tectonics provided the heat and pressure to create the Sierra. It provided the movement to raise and lower the land masses. Low-angle thrust faults created our Coast Range and the Sevier-type thrusts created our Rocky Mountains but the heat and pressure of the plates created the Sierra Nevada. The range is the largest batholith of granite in the world. A batholith that is 80 miles wide and 400 miles long.

130 Million Years Ago

This is what the Sierra Nevada looked like about 130 million years ago. Most of the Sierra was within Nevada.  A. The northern Sierra with Volcanic activity,   B. The Northern Coast Range,  and C. The Mid-Continental Seaway.

 

50 Millions Years Ago

About 50 million years ago extreme uplift and compression caused by plate tectonics created A. the overlapping Rockies with numerous shear faults. B. The Sierra lifted upwards along it’s eastern block boundary with slippage faults creating large westward drainages. The arrow points to the ancestral Yuba River System. C. The Coast range was an accretionary complex of sedimentary materials pushed upwards.

 

5-10 Million Years Ago

By 5-10 million years, you start to recognize the A. Sierra uplifted as a range and moved westward by the dropping of the C. Basin Range of Eastern Nevada. B. The coast range continues to rise and the Transverse Range appears.

 

Geology

Laurel Mountain near Mammoth contains some of the earliest rocks within the Sierra. Within these areas you can see the early geologic formation of the Sierra with the sedimentary layers of ancient seabeds that are folded into a metamorphic formation. The sediments were deposited in a deep water basin about 500 millions years ago and gradually became a shallow sea about 350 million years ago.

The Sevehah Cliff on the eastern side of Laurel Mountain at Convict Lake shows the marble formed through metamorphosed sedimentary rocks during the Paleozoic age.  An example of the earliest rocks within the Sierra formed over 200 million years ago.

Ancient Shallow Sea

California was an ancient seabed 500 million years ago. Over 12,000 feet of sand, silt, and mud were deposited. The weight of this material created sedimentary layers. Forces within the earth pushed these layers above ground where they were exposed to erosion. The land sunk and rose at least three times, where the last land push above water was about 100 million years ago. This was in conjunction with volcanic activity which laid volcanic rock above the sedimentary layers. Most of the glacial and erosion processes eliminated the younger volcanic material, exposing the granite that continues to be pushed upwards by heat and pressure.

 

Roof Pendants

Within the Mammoth region, many mountains retain the older sedimentary rock. Mt. Morrison is a roof pendant next to Convict Lake.  It is metamorphosed limestone consisting of Dolomite and Marble.  The mountain has colors of White, Yellow, Orange, Red, and Brown. The age of the rock is Pre-cambrian making it one of the oldest rocks within the Sierra.

The top of Mt. Morrison is Mt. Morrison Sandstone from the Devonian Age, about 350 million years ago. Paleozoic fossils can be found on the summit.

 

 

Defined by Paul C. Bateman [1992], a roof pendant is "A mass of metamorphic rock that is entirely surrounded by plutonic rock and presumed to be a downward projection of rocks that overlaid the plutonic rocks before erosion." As massive amounts of granitic magma rose to the surface, subsequent uplift, tilting, and erosion exposed the large spire shaped peaks that are the roof pendants. The steep structures present today that are referred to as roof pendants are the remains of igneous and marine sedimentary rock formed during the Paleozoic and early Mesozoic age.

 

Granite Batholith

The magma melted existing rock and caused new minerals to crystallize in the overlying sedimentary and volcanic rock, depositing veins of gold, and creating metamorphic rock. The molten material deep below the sedimentary, volcanic, and metamorphic rock cooled and formed the granite batholith of the Sierra Nevada about 65-225 million years ago, 400 miles long, 70 miles wide. The Sierra Nevada mountain range is an enormous deposit of granitic rock, forming the largest mountain range within the contiguous United States.  Over the last 1 million years, there have been 6 episodes of glacial advance and retreat, the last being 15,000 years ago. This activity has removed the upper layers of rock and exposed the granitic core, polishing the granite to a smooth surface.

 

Balloon Dome, Ansel Adams Wilderness, San Joaquin River Canyon. Note the marshmallow effect (plutons) of the granite forming within the magma and floating to the surface with uplifting. The overlying rock is eroded away exposing the granite. The granite erodes in concentric layers like an onion.

The Needles, unglaciated granite spires near Forks of the Kern.

 

Mt Aggie and Mt. Baldwin from McGee Canyon. Note the folded volcanic and sedimentary layers, Shale and Sandstone and  Granite batholith. Roof Pendants are on the top of the peaks with seabed fossils. The wide valley with moraines created by glaciation.

Volcanic Activity

Volcano activity started about 30 million years ago along faulting events. About 5 million years ago, the Sierra uplift began to rise and another increased period of volcanic activity started about 3 million years along the parallel faults bringing gold, silver, and other minerals to the surface.

Examples:

Mono Lake – Series of cinder cones, most recent eruption was Paoha Island about 230 years ago.

Mono Craters – Lava domes and cinder cones, most recent eruption about 600 years ago.

Inyo Craters – lava domes, 15 explosion craters, last eruption about 600 years ago.

Mammoth Mountain – lava dome complex. Last eruption was 57,000 years ago. Increased seismicity, gas emission and tree kill occurred in 1989.

Golden Trout Creek – Volcanic field of Cinder cones and lava flows. Most recent eruption 5,000 years ago.

Bishop Tuff

Bishop Tuff is a welded ash from an eruption of the Long Valley caldera 760,000 years ago. It was a Rhyolitic pyroclastic flow covering over 850 sq miles with a thickness ranging from 490 feet to 660 feet. You can view this along Chalk Bluff Road at the Lower Owens river at the "Wild Trout" section.

Glaciation

Over the past one million years, cycles of cooling and warming have brought at least six episodes of glacial advance and retreat. The last ice age in the Sierra Nevada Range ended about 15,000 years ago during the Pleistocene era, with glaciers receding from the main canyons. A minor episode of climatic cooling caused the Little Ice Age from about 700 to 150 years ago, when most of today’s glaciers were formed.

 

Six Glacial Periods of the Pleistocene  1.8 Million to 10,000 years

• McGee 2700-1500 ka Late Pliocene
• Sherwin 820 ka, late Early Pleistocene
• Tahoe 50-42 ka,
• Tenaya 32 ka
• Tioga 25-16 ka
• Matthes 0.6-0.1 ka

KA is Pottasium/Argon dating of glacial deposits

 

 

A minor episode of climatic cooling caused the Little Ice Age from about 700 to 150 years ago, when most of today’s glaciers were formed. About 100 glaciers have been identified. They reached maximum size by 1750 and started most of their retreat in the 1930’s.

Moraines

Moraines are easily observed along the Eastern side of the Sierra. There are two types of Moraines, Lateral which occurs along the side of the glacial movement and Recessional which occurs at the base of the glacier.

Climate Change

For the last 10,000 years, the Sierra Nevada has had wet winters and dry summers.  There were two droughts over the last 1200 years, each lasting 100-200 years.

Little Ice Age occurred from 1250 to 1350 AD bringing the Sierran Glaciers to the same positions as the last major Ice Age 10,000 years ago.

The last 150 years has been warm and wet with the wettest 50 year period of the Sierra during this time period over the last 1000 years.

Sierra Nevada Climates

EH – above 12,000’, Severe Winters,      avg temp (warmest month) 50F

Dsc – 9,000 to 10,000’, Cool Dry Summers, Cold Snowy Winters, avg temp (warmest month) below 71F

Dsb – 7,000 to 9,000’, Pleasant Dry Summers, Cold Snowy Winters, avg temp (warmest month) below 71F

Csb – 3,000 to 6,000’, Pleasant Dry Summers, Rain & Snow mix Winters, avg temp (warmest month) 71F

Csa – Valley Floor to 3,000’, Hot Dry Summers, Mild Winters, avg temp (warmest month)  above 71F

Bsk – Eastside 5000 to 7000’, avg temp (coldest month) below 32F

Bsh – Eastside 3500 to 5000’ and Westside of Southern Sierras below 500’, avg temp (coldest month) above 32F

Image Courtesy of Anthony Dunn Sierranevadaphotos.com

 

Average Snow Depth

Snow is a dominant force in regulating the seasonal distribution of water through the Sierran river systems. Snow pack tends to decrease from North to South and is lower on the east side than the west side. Snow accumulations tend to increase with elevation and the higher elevations of the Central and Southern Sierra will have the greatest snow depths.

Image Courtesy of Anthony Dunn Sierranevadaphotos.com

 

The Sierra Nevada generates about 20 million acre feet of water runoff each year. This is about 30% of the State’s total. 50% of the rainfall occurs during the winter, 33% in the Fall, 15% in the Spring, and 2% in the Summer. On the westside, about half of all precipitation becomes streamflow, the other half accumulates as snow.

Image Courtesy of Anthony Dunn Sierranevadaphotos.com

 

Floral Diversity

There are over 3500 native species found within the Sierra Nevada, making up 50% of the state total in plant diversity. Distribution of wildlife is closely associated to the distribution of vegetation. The conifers start at 1,000 to 3,000 feet elevation on the western slope and 3,000 to 5,000 feet on the eastside. Ponderosa Pine dominates the lower western slopes going up elevations to Douglas Fir, White Fir, Sugar Pine, and Incense Cedar. The Eastern Slope starts with Pinion Pine/Juniper, then Jeffrey Pine and Ponderosa. Firs inhabit the upper elevations of range starting with White Fir, then Red Fir. An alpine zone of conifers will include Mountain Hemlock, Lodgepole, and Western White Pine. The extreme reaches of conifers will be Whitebark Pine, Foxtail Pine, and Western Juniper.

Major vegetation zones form north-south along the axis of the range. Only part of the Sierras is forested, other areas are meadows, chaparral scrub, Oak woodland, savanna, Canyon land, alpine habitat, bare rock, and water.

 

Human Impacts

Water Quality

The Sierra Nevada has provided high quality water for communities throughout the state. Water Quality issues have become worse over the last forty years with Giardia (human pathogen) present in almost all streams and lakes, accumulation of near toxic levels of mercury in many low to middle elevation reservoirs from mining activity, and increased salinity on eastside lakes due to water diversions.

Agriculture

Agriculture was a major source of employment within the Sierra throughout the early 1900’s. The total number of irrigated acres within the Sierra in 1920 is the same as today. Human activities such as agriculture, mining, logging, and grazing has been practiced extensively over the last 150 years, particularly within the mid and lower elevations. Human activities have led to an increase in fire suppression, diversion of water, road building.

Mining

Mesozoic deposits (100 million years ago), altered by pressure and heat, formed gold and silver that was discovered deep underground or exposed through erosion. This began the first influx of Euro-Americans into the Sierra beginning in the 1850’s. Mining has had a significant impact on streams. With the increased price of gold and silver, many of these mining claims are being reexamined for feasibility of extraction.

 

Ground Sluicing (1851-1859)

Hydraulic Mining occurred in 1860-1890. Most hydraulic mining occurred on the Feather, American, Bear, and Yuba Drainage. An 1880 estimate by the  Calif. State Engineer was 680 million cubic yards of debris was created and washed.

Logging

Photo : Yosemite Logging Company No. 4 1920-43

80 Timber mills in 1855, 320 mills by 1860.

Most mills were located in Northern and Westside Sierra.

Nearly all virgin forests of Tahoe/Truckee were removed between 1856 and 1880.

Sawdust was dumped into local streams.  This procedure ended by 1894.

 

In 1970 there were about 200 Timber mills in the Sierra Nevada. Today, there are only three.  Recent USFS Surveys indicate that there are about 12 million dead trees within the National Forest of California due to poor forest management.

The declining health of Sierra Nevada forests is not expected to improve any time soon. After decades of fire suppression and limited forest-thinning operations, trees are choked with competition and starving to death, deprived of sufficient water and nutrients and impoverished by drought. Taking advantage of their vulnerability, bark beetles and other invasive insects move in for the kill—then repeat the process in neighboring trees.

Fuel-removal projects and controlled burns are needed to mitigate the issue, researchers say. But resources among cash-strapped local, state and national agencies are too scarce to even scratch the surface in most areas. Compounding the problem, the Sierra Nevada does not have the infrastructure—such as sawmills and biomass plants—to process a large amount of material.

Aquatic Habitats

Aquatic and Riparian habitats are fundamentally dependent on natural flows of water. These habitats have had to change due to human activities in regulating water flow. 40 species of fish are native to the Sierra, 6 are listed as threatened or endangered, 12 others are candidates for listing. Less than half of the native fish species within the Sierra have secure populations.

Fish Introductions

During the 1800’s there were occasional transfers of fish in buckets. Today, CDFG has ten hatcheries to raise trout producing 13 million “catchable trout”, 1.2 “subcatchable”, and 12.3 million “fingerlings”. About 35 non-native fish have become established within the Sierra with 10 species becoming widespread and abundant. Brook Trout and Brown Trout were introduced in 1872, Lake Trout in 1889, Kokanee in 1941, Colorado Cuts in 1931, and Arctic Grayling in 1930.  Large introductions were made by Calif. Fish & Game through aerial planting during the 1950’s and 60’s to cover about all of the 4,000 natural lakes within the Sierras. Today, about 2,000 lakes are planted and none within the National Parks. Invertebrates and amphibians have been greatly impacted by the fish introductions. All fish planting was discontinued with Kings, Yosemite, and Sequoia National Park by 1980. About 40% of the lakes within the parks have become fishless once again.

Population Growth

The population within the Sierra Nevada in 1990 was 650,000, this is expected to triple to 1.8 million by 2040. 70% of the total population live on the westside. Past population growth were based upon resource extraction, ie mining, logging, grazing etc. New populations tend to be retirees, commuters, and ex-urban migrants. The age structure is increasing and wealth is being brought into the area from outside the region. There will be less emphasis on resource extraction with the exception of water.