Ca Geology Chp 8 Sierra Nevada

Front 1

Sierra Nevada mountains are responsible for the rain and snow dumped by Pacific storms. Without the Sierra Nevada's __, couldn't support people here.

Back 1

water;

Hint 1

Yosemite, Sequoia, Kings Canyon National Parks here.

Front 2

The __ imaginary line connecting the summits & highest parts of the mountains are highest in the __ with Mt. Whitney and lowest in the ___. The lowest places have passages.

Back 2

crest;

south;

north;

Hint 2

Interstate 80

Front 3

Uplift and __ tilting cause the asymmetry of the Sierra Nevada and produce the ___ western slopes unlike the __ eastern slopes. Partly because of Basin & Range normal faults.

Back 3

westward tilting;

gentle;

steep;

Front 4

__ is a river valley that becomes resistant to erosion when a volcanic eruption fills it with lava. As the surrounding area erodes, the sediments of the river channel beneath the rock forma flat-topped, river shaped mountain. This creates an __ topography, A landscape in which areas formerly low are now at the highest elevations.

Back 4

table mountain;

inverted topography

(Sonora, San Joaquin Table Mountain & Oroville Buttes)

Hint 4

Front 5

Sierra Nevada mountains are geologically __ while the rocks are ___ coming from past Mesozoic mountains.

Back 5

young; older;

Front 6

Sierra Nevada is mostly __ plutonic rocks (always on the west) with some __ in the east. __ refers deep plutonic rocks crystallized from different magma. Most of the rocks are __ composition (high silica) with granodiorite being the most common.

Back 6

Mesozoic;

Paleozoic;

Batholith;

granitic;

Front 7

The depth at which the magma solidifies within the surrounding rocks is the __ depth of a pluton. One way to determine this is using metamorphic minerals as ___ that can be a reliable indicator of the depth at which magmas were emplaced since they form at certain temperatures & conditions.

Back 7

emplacement;

geobarometers or geothermometers;

Front 8

Plutonic rocks in the __ of Sierra Nevada are mafic very metamorphic and formed deeper in high pressure and temperatures. Mostly Mafic gneiss. Sometimes hard to tell apart from igneous rocks. Have the roots of the batholith. smooth, rounded granitic slopes.

Back 8

south;

Front 9

__ has dark jagged pinnacles black slate and metamorphosed volcanic rocks.

Back 9

North;

Front 10

Discovered ___ large caldera like Long Valley caldera.

Back 10

Minarets caldera;

Front 11

Batholiths form at ___ areas water catalyst heats basaltic magma rises and mixes with large amounts of silica rich magma, generating the batholith-forming granitic magma. Some magma rises to the Earth's surface with less mixing, producing andesitic lavas of volcanoes like the Andes or Cascades.

Back 11

subduction;

Front 12

__ Cretaceous plutons in the western Sierra Nevada and __ in the eastern. Outside of Cretaceous period, oldest rocks are in the __.

Back 12

older; younger;

east;

Front 13

Most volume plutons in making __% of batholith is 120 to 80 million years ago in Cretaceous period. Episodic. Rapid subduction.

Back 13

90%

Front 14

The angle of subduction flattened out. This change of geometry, the zone of magma generation shifted to the east "shutting off" the Sierran batholith and triggering ___ activity to the east.

Back 14

magmatic;

Front 15

Sierra Nevada is mostly granitic rocks, but some metamorphic. ___ are blocks of metamorphic rocks. septa is roof. Western metamorphic belt along the NW foothills interesting because they are the host rocks for CA's __ deposits.

Back 15

Roof pendants; Gold;

Front 16

Majority of metamorphic rocks only moderately metamorphosed. Many __ showing evidence of metamorphic layering caused by the growth of metamorphic minerals in preferred orientations.

Back 16

foliated;

Front 17

Metamorphic rocks of Sierra Nevada 4 groups.

Back 17

1. Paleozoic North American Plate Metasedimentary rocks related to Basin & Range.

2. Mesozoic metavolcanic erupted on North American Plate.

3. Paleozoic Metavolcanic & metasedimentary rocks ancient volcano arc accreted to North America.

4. Paleozoic & Mesozoic Metavolcanic & metasedimentary rocks acreted to North America during Mesozoic.

Front 18

There is are two extensive bands of metamorphic rock on the western metamorphic belt.

Back 18

k

Front 19

The Shoo Fly Complex are the oldest rocks in the northern Sierra Nevada 1900s. Oceanic origin. variety of metamorphic rocks

Back 19

Shoo Fly Complex

Front 20

The ___ is a younger belt of Paleozoic rocks and includes chert, black shale, radiolaria. Permian time andesite erupted here. Some of the metamorphosed limestone have unique fossils of reefs from the here and the Klamath mountains. These two areas are believed to have been continuous & part of a series of island arcs during the Paleozoic times.

Back 20

Northern Sierra Terrane;

Front 21

The ___west of northern Sierra terrane are separated by a major fault system. It has complex assemblage with:

1. Submarine volcanic rocks erupted at spreading centers.

2. Sedimentary rocks deposited in deep-ocean trenches;

3. Metamorphic & plutonic rocks formed at great depths within & beneath the crust.

In the northern Sierran foothills, rocks within this belt have been named the ____.

Back 21

subduction complex;

Calaveras Complex;

Front 22

The westernmost belt of metamorphic rocks in the Sierra Nevada are the ___ and represent the youngest period of subduction & accretion in the Sierra Nevada.

Back 22

Foothills Terrane;

Front 23

Caves formed by dissolution of ___ rock due to water flowing along fractures. Calcite. All of the caverns in the Sierra Nevada have formed in the metamorphic rocks of the accreted terranes, in the metasedimentary blocks composed of marble. Mercer and Moaning Caverns.

Back 23

carbonate;

Front 24

Mariposite apple green mineral creating mariposite shcist a banded green & white rock. Can contain gold bearing veins. Used to represent CA in Consitution Monument built in Philly for 200th anniversary of Constitution & Bill of Rights.

Back 24

Mariposite

Front 25

1848 James Marshall discovers gold near Sutter's Fort Sacramento. Nuggets. American River.

Back 25

45% of world's gold output.

Front 26

Most gold pure "native" rather than combined with other elements to form gold-bearing minerals. Gold forms veins of quartz 30 cm to 30 m thick. A continuous zone of gold-bearing quartz veins is the ___ along Melones fault.

Back 26

Mother Lode;

Front 27

Gold mostly in metamorphic, but granitic too. __ mining district richest & most famous in CA. $300 million. __ Mine richest producer of all mines $130 million.

Back 27

The Grass Valley mining district;

The Empire Mine;

Front 28

Sedimentary ore deposits in beaches and rivers are known as ___. 40% of CA's total gold output was found like this. Gold resists weathering so lasts a long time.

Back 28

placer deposit;

Front 29

Early gold miners used __ a technique used to extract gold from river sediments by swirling the sediment in water using a round, shallow dish.

Back 29

panning

Front 30

Miners then used ___ a long box mounted on rockers and used to sort placer golds from river sediments. 1848

Back 30

Rocker or Cradle

Front 31

1849 A large version (12 ft) of the rocker used to separate placer gold from silver sediments.

Back 31

Long tom

Front 32

A long open wooden trough box with a series of riffle boxes, fitted with cleats to catch the heavy sediment. (gold heavier/denser sediment)

Back 32

Sluice box

Front 33

1850s constructing ditches & flumes to move enough water to run their sluices. These water diversions had lasting effects on CA water laws.

Back 33

kk

Front 34

Gold washing didn't always completely separate gold from other heavy minerals. Used __ which binds gold in an amalgam. Heat it and the __ vaporizes leaving behind pure gold.

Back 34

mercury; mercury

Front 35

After searching entire beds more than once and overturned, and diverting rivers, miners looked to older placer deposits known as __ gravels.

Back 35

Tertiary gravels;

Front 36

To get to deep Tertiary gravels, miners attached a nozzle to a hose & forcefully washed the sediments down from hillsides and changed the landscape with ____. Lots of sediment got into Sacramento Valley & SF-San Joaquin delta affecting navigation & AG. Sawyer Decision 1884 banned dumping of sediments there.

Back 36

Hydraulic mining;

Front 37

__ extract sediments from riverbeds. Floating suction __ are able to remove sediment for gold washing while the rivers are flowing, thus eliminating the need for diversion. Great piles of sediment are known as __.

Back 37

Dredging; dredges;

dredge fields;

Front 38

Mining Lode deposits of quartz veins are difficult because underground. ___ device used to pulverize the quartz with a heavy iron pounder. Gold was then sorted using mercury & sluices. Stopped in 1940s.

Back 38

stamp mill

Front 39

__ mine poor ventilation & wooden timbers 1922 fire killed 47 miners.

Back 39

Agronaut

Front 40

Two famous gold finds are the __ pound mass at Carson Hill & __ pound pure gold nugget found at Magalia.

Back 40

195 pound mass;

54 pound;

Front 41

Today mining companies are using a chemical process called ___ to extract gold from deposits that have not been profitable in the past.Gold recovery by 100 times over other methods. 16 mines still active in 2001.

Back 41

heap leaching;

Front 42

Any accumulation of a particular element including metal like gold, silver, mercury, that has been sufficiently concentrated to be profitably mined.

Back 42

ore;

Front 43

During __ between 28-22 mya, hug ash flows from Great Basin covered Mesozoic rocks in part of the Sierran Province and deposited the Valley Springs Formation in Sierran foothills. Younger andesitic volcanoes erupted 9-11 mya from high Sierra Nevada to deposit the Mehrton Formation in west Foothills, Table Mountain flows.

Back 43

Cenozoic;

Front 44

__ are responsible for much of the landscape of the High Sierra and has left a record of the Sierra Nevada's past climate. It's a body of ice that moves over a land surface. increases 9X density and strength 50X.

Back 44

Glaciers;

Hint 44

Retreat is when glacier shrinks. Accumulation area at high elevations and ablation area at lowest points because temperatures are lower at higher elevations.

Front 45

Climate fluctuates. During Pleistocene, mountain ranges such as Sierra Nevada covered by ___. Continent needs to be near poles and uplifting. Tilt, orbit, & solar sunspot affect amount of solar radiation. Glaciation __ sea level.

Back 45

alpine glaciers; lowers;

Front 46

3 factors influenced glaciers along Sierra Nevada.

Back 46

1. Ranges lower in North so smaller glaciers.

2. South warmer so glaciers restricted.

3. Snowfall greater on west than east because rainshadow effect.

Front 47

Largest glacier today is Palisade glacier.

Back 47

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Front 48

As moving glaciers dragged rock fragments over vast areas of bedrock, they created scratches called glacial ___, grooves crescent shaped gouged marks, & a very shiny glacial polish. Tioga Pass.

Back 48

Striations

Hint 48

Front 49

On a larger scale, granitic mounds called ___ were streamlined underneath ice, leaving asymmetrical domes that point in the direction of ice flow.

Back 49

roche moutonees;

Hint 49

Front 50

Bowl shaped depressions that the ice has carved at the head of glacial valleys. These elevations help give estimates of the ancient position of the snow line during glacial periods. Snow line was 750 meters lower than it is today.

Back 50

cirques

Hint 50

Front 51

A glacial valley whose mouth is much higher than the elevation of the valley it joins. More of a U shape steep sided and broad bottemed. Waterfalls of Yosemite are a great example.

Back 51

hanging valley

Hint 51

Front 52

The peeling off of the outside surfaces of massive rocks such as granite from the release of pressure of uplifting. Responsible for dome formation in the Sierra Nevada.

Back 52

exfoliation

Hint 52

Front 53

Glaciers deposit ice transported boulders ___ dumped on glacially polished surfaces and ___, piled ridges of sediment along the sides of a valley glacier. These are composed of material pushed along by the glacier and left behind after the ice melted. This poorly sorted material can contain huge boulders & is called glacial till.

Back 53

Erratics;

Moraines;

Hint 53

Front 54

Moraines and till help to reconstruct the extent of glaciers that have long since melted. Sierran glacial deposits difficult because not completely preserved & because contain very little datable organic material. West side little preserved, but east with rain shadow has some.

Back 54

kkkkkkk

Front 55

Most recent glaciation periods are __ glaciers and ___ glaciers with the latter being older. Evidence of an older one called Sherwin glaciation.

Back 55

Tioga glaciation;

Tahoe glaciers;

Front 56

__ is the 2nd deepest lake in the U.S. 501 meters deep. 1,897 meters above sea level. Lies within a down-dropped basin created by late Cenozoic faulting & Pleistocene glaciers. Has naturally clear water because sand sized sediment & lacks nutrients. However, algae is ruining it now.

Back 56

Lake Tahoe

Front 57

At beginning of ___, 230 mya, subduction started and changed CA's plate tectonic setting. As a result, granitic magma crystallized within the North American plate forming the oldest plutons of the Sierra Nevada Province about 210 mya.

Back 57

Mesozoic

Front 58

As subduction continued, pieces of oceanic plates were accreted to the western edge of North America. Although subduction & accretion occurred during Mesozoic time, the eastern accreted terranes contain Paleozoic rocks. West part of the Sierra Nevada foothills are made up exclusively of Mesozoic rocks.

Back 58

kkk

Front 59

100 mya subduction moved westward to today's Coast Ranges. At this time, most plutons in Sierran batholith crystallized from magma. 100-80 mya, giant andesitic volcanoes formed a mountain chain in today's Sierra Nevada. Enplacement of the Sierra batholith metamorphosed both the rocks of Paleozoic North American & the rocks of the accreted terranes.

Back 59

kkk

Front 60

At the end of the crystallization of the batholith, __ was concentrated in quartz veins emplaced in the rocks of the western Sierran foothill.

Back 60

gold

Front 61

During late Cenozoic 9-10 mya, major volcanic eruptions from sources close to Sierra Nevada produced lava flow that went into east rivers. Buried ancient river gravels some which contained placer gold deposits.

Back 61

Cenozoic

Front 62

Following the discovery of gold in 1848, miners from all over the world swarmed into the ___. Hydraulic mining washed millions of tons of sediment into the Sacramento River between 1850s & 1883 when it was banned. Changed landscape.

Back 62

Sierran foothills