New EART-3: Module 6-8

What is the topography of the Basin?

- elongated mountain ranges - that repeatedly descend into flat and dry desert The mountain ranges in this park are representative of uplifted fault block while the basins are corespondents of down dropped fault block. These faults are identifiable by the thick sediment wedges that are divided from the surrounding ranges.

How did the Ancestral Sierra Nevada form (Mesozoic Batholith)?

1. 200 m.y ago the Farallon plate began to subduct 2. then 140 m.y. ago, water had been driven off and from the subducting Farallon plate to melt rock in the overlying mantle, which then rose toward the surface. 3. Magma then forced its way into the crust of the growing mountain belt along the continental edge 4. magma that leaked upward to erupt from the chain of volcanoes marked the crest of these ancestral Sierra Nevada. 5. However most of the magma that stayed underground, cooled and formed networks of magma chambers. 6. then from about 140 to 80 m.y. ago, several generations of magma chambers pushed their way into the ancient mountain chain (along the western continental margin), creating what we today call the Sierra Nevada batholith ---------------- Batholith: a hundred or more plutons overlap with one another and collectively form a larger mass of granitic rock called a batholith.

why are volcanos no longer active in SN NP? (Ancestral Sierra Nevada )

1. About 80 million years ago, a change in the plate-tectonic setting shut off magmatism and volcanism in the Sierra Nevada. 2. Without the intrusion of magma at depth, the chambers cooled and formed the very youngest plutons. 3. At this point, the ancestral Sierra had reached their peak of uplift. the rate of erosion outpaced the slowing rate of uplift and the mountains began to wear away. 4. The erosional debris was swept downslope into the nearby ocean, filling a basin that today is the Central Valley of California

Features of plate convergence:

1. Accretionary wedge: the package of sediments that gets scrapped off the oceanic plate, piles up and deforms to build the accretionary wedge. 2. volcanic arc: built by fluid-flux melting is a feature of subduction zones- The Cascade volcanoes and the Sierra Nevada Provinces are found in this environment. 3. convergent margin: the deformation of rocks that occurs behind the volcanic arc in the region often called the Foreland Fold and Thrust Belt- tectonic setting of the Rocky Mountains.

Two general regions of Alpine Glaciers:

1. At the highest elevations where the glacier begins (also known as the 'head' of the glacier), the area is called the 'zone of accumulation.' Accumulation: If the rate of accumulation at the head exceeds the rate of ablation at the toe, the glacier advances downslope- happens during phases of colder climates. Process: Snow falls and accumulates to some thickness, if summer is not warm the snow becomes compacted- cycle occurs over a period of years. The dense snow particles then begin to recrystallize into solid ice with most of the air forced out by the pressure. The mass of the ice becomes then great enough that the glacier begins to flow downhill under the force of gravity. ------------------------------ 2. At the lowest endpoint of the glacier (also called the toe or the terminus), the temperatures are commonly warm enough that the ice begins to melt. This creates meltwater streams and meltwater lakes along the toe of the glacier. Ablation: If the rate of ablation exceeds the rate of accumulation, the glacier retreats upslope by loss of ice at its toe- happens during interglacial warm phases. it appears to move upslope way due to melting and loss of ice at the toe. Process: is the decay of glacial ice by melting, sublimation, and physical breaking is collectively called ablation. If the toe ends in an ocean or lake it breaks off in the form of an iceberg. ------------------------ Terms: The ice at the terminus may also vaporize directly into the atmosphere in a process called sublimation.

Rock formation process in Sierran national parks (granite cliffs):

1. Jointing: a. sets up the rock for further weathering and erosion by weakening the rock, leading to rockfalls. b. Jointing also permits the penetration into the rock by water that freezes, allowing for the plucking of large blocks of rock by an over-riding glacier. --------- 2. Rockfalls (most prevalent in SN): joint planes penetrating all the way through the body of the rock, weaken the rock/cliff faces along the vertical joints and create a gigantic vertical slab, that breaks away and crashes down as a rockfall (the rapid movement of rock and soil) .-------------------- 3. Glaciation: Glaciers are essentially rivers of ice that flow downslope under their own weight and scour the debris left at the bottom of cliff faces by rockfalls... bulldozing the loose rock downslope and grinding it up into smaller fragments that may be carried off by meltwater streams.

What are the 2 phases of the Sierra Nevada?

1. Mesozoic phase when the granitic plutons were formed 2. and a modern Sierra that we see today. Plutons that were first formed, were uplifted to the surface by mountain-building processes and exposed to weathering and erosion. Today the originally molten masses of rock deep beneath the surface of the ancestral Sierra Nevada are with waterfalls flowing over the surface and random veneers of soil and vegetation. --------------- The magma chambers that would eventually become the individual plutons fed numerous volcanoes that marked the crest of the ancestral Sierra Nevada during the Mesozoic.

Rocky Mountain landscape:

1. Rockies rise above the high plains of the Midwest 2. comprise the eastern flank of a wide and extensive set of mountain belts. ------------------------ The continental divide and the rocky: 1. snakes along the Rockies -------- 2. and travels right through Rocky Mountain -------- 3. and Glacier National Parks. The park includes a triple divide with some streams flowing: a. west toward the Pacific, b. some flowing southeast toward the Gulf of Mexico c. and others flowing northeast eventually to drain into Hudson Bay.

Glacial landscapes of national parks of the Sierra Nevada:

1. U-shape valleys: Alpine glaciers tend to flow downslope through former stream valleys. Glaciers act to reshape the V-shape stream valley into a U-shape as they grind away at the bedrock on their way downslope. ---------- --------------- 2. Cirques: form at the heads of glaciers by plucking of rock along both the steep headwall as well as from the underlying bedrock at the base of the growing glacier. Identifiable: they open up downslope into U-shaped valleys that mark the path of the former glacier. They are bowl-shaped depressions bounded by steep-walled cliffs. ------------- 3. arête: is an erosional remnant left behind as glaciers physically scoured the rock from both sides. Identifiable: by the margins between two adjacent cirques. They may consist of a narrow, knife-like ridge of bedrock. 4. Tarns: form as the last remains of a glacier melt. These tarn lakes may form in the lowest depression within the bowl-shaped cirques. 5. glacial striations, seen at surface level (not the same as deeply embedded joints): Fragments of rock and sandy sediment act like a rasp on the underlying bedrock, leaving behind striations as erosional scars. Striations reveal the former direction of movement of the glacier. 6. Erratic: Are huge boulders left behind on a bedrock surface as glaciers melt. The erratic is the debri left behind in the wake of the glacier. They are composed of a different rock than the bedrock beneath. They are also used to trace the origins of the glaciers that carried them down the valley. 7. hanging valley: With warming, glaciers melted and receded upslope, the side valleys were left hanging above the deep main valley. Meltwater streams that drain these hanging valleys tumble over in waterfalls down to the floor of the main valley. --- process: Prior to glaciers, the original river system consisted of a main stream fed by tributaries that drained the high country. During global cold phases, alpine glaciers occupied the drainage system, with tributary glaciers feeding downslope into a main glacier.

Landforms in Sierran national parks:

1. Vertical cliffs: El Capitan, has a vertical face, or the exposed surface of a vertical joint plane. Surface exposure was created by several ancient landslides and rockfalls due to erosion. 2. Domes: the back side of Half Dome is marked by numerous overlapping sheet joints (exfoliation jointing). You can see the scars left behind after the sheets cracked and broke away, slipping downslope in massive ancient rockfalls. 3. monoliths: Moro Rock, in Sequoia NP, The monolith is relatively free of vertical joints the domal shape is a product of: a. exfoliation b. jointing c. rockfall ....of sheets of granite from the onion-like outer surface. how did dome form? 1. Glacier in Tenaya Valley scoured the rock at the base of the dome, leaving an overhanging mass of granite projecting above the valley floor. 2. Rock mass then broke off in a rockfall along a single joint surface.

3 National Parks in the Rocky Mountain Province:

1. Yellowstone National Park in Wyoming 2. Rocky Mountain NP in Colorado 3. Glacier National Park in Montana.

Parts of a fault: hanging wall and footwall(Rocky Mountains)

1. hanging wall/ normal fault: is the block miners hung their lanterns on above the fault- This occurs in tensional tectonic environments normal fault: break in rock caused by tension forces, where rock above the fault surface moves down relative to the rock below the fault surface 2. footwall: block that the miners walked on, below the fault

How to identify active normal faulting?

1. look for straight boundary along the base of the range. 2. Look for a triangular faucet of the mountain face. 3. Look at the valleys. If they have a wine glass shape, a v-shaped erosion, tiene un weco. 4. Alluvial fans

Laramide mountain building in collisional environments?

1. mountain building typically involves the collision of 2 tectonic plates. 2. which then initiates with subduction of an oceanic plate beneath another oceanic plate or a continental plate- also called Andean style after how the Andes where formed in South America.

Some of the challenges and hazards of hiking on glaciers in Yosemite National Park are:

1. rockfalls 2. rockslides 15 people have died from rockfalls in the last 150 years

Geological history of the Rocky Mountains:

1.Began Late Precambrian mountain building Mountain building a. folded, b. faulted, c. uplifted, metamorphosed, and melted pre-existing rocks. however, these Precambrian mountains were eroded and the igneous and metamorphic now make up the basement rocks of the Colorado Plateau and cores of Rocky Mountains. ----------- 2. During Paleozoic Era, western North America was at or below sea level, the period is dominated by marine sedimentation. Reason for thick Paleozoic marine sedimentary rocks on the Colorado Plateau, Grand Canyon NP and on the flanks of the Rocky Mountains. ---------------- 3. Mesozoic era, land emerges and rock is dominated by non-marine sedimentation. History is contained in rocks at the flanks of the Rocky Mountains. ----------------------------------- 4. Late Mezizoic- Early Cenozoic The uplift of the present Rocky Mountains is a result of the Laramide mountain-building, ran from the latest Mesozoic into the beginning of the Cenozoic (about 70-35 million years ago). episode was caused by compressive forces generated by subduction off the west coast of North America. a. These forces squeezed, bent, and faulted the rocks, b. uplifting old Precambrian buried rocks c. eroding off the younger rocks that sat on top d. and exposing the old rocks at the surface.

What kind of subduction zone dominated western North America during the Mesozoic? (Ancestral Sierra Nevada)

A convergent, Cascadia-style subduction zone: the Farallon oceanic plate was subducted under the continental plate at one time

The continental divide?

A drainage boundary, a place on a continent that separates river systems flowing in opposite directions

Reverse Fault (Thrust Fault)

A fault in which the hanging wall rises relative to the footwall. It is caused by compression. - This type of fault has the potential to turn sediments upside down - stack older sediments on top of new ones - and cause sedimentary sequences to break apart along the low angle reverse faults This type of fault is evident along the western margin of North America.

How do magma chambers form?

A magma chamber is nothing more than a reservoir of molten rock. It permits replenishment of magma from sources deep below and also releases magma from the top to supply volcanoes at the surface.

transform boundary

A plate boundary where two plates move past each other in opposite directions

Glaciers Yosemite national park video:

Active glaciers in sierra nevada are only found in highest elevations near the peaks and the range and in cirques that face North or Northeast. ----------- Unfortunately they are actively retreating due to: 1. globally changing climate, everybody is of responsible As temperatures get warmer, animals, plants and glaciers will disappear- in a few decades --------- Active glaciers in the crest of the Sierra: 1. Lyell Glacier is in alpine zone- no friendly to humans. It is the highest point of Yosemite National Park, second largest glacier in sierra nevada, and is over 13,100 feet 2. Maclure Glacier, has crevasses. They are big fissures that forms as the glacier is moving down slope. It moves about 20 feet a year The toe of the glacier is an ice cave. ---------------- DANGERS: 1. Ice is moving 2. rocks are moving 3. moraines are fairly unstable, loose rocks 4. down slope side will move a little bit faster than the upslope side 5. crevasses: big fissures that forms as the glacier is moving down slope. Formed from millions and millions of snowflakes slowly working on the mountainside, sliding downhill.

Glaciation in the Sierran national parks:

Alpine glaciers are also called mountain glaciers and, valley glaciers. They tend to flow downslope. ---------------- How do they flow? 1. Glaciers are essentially rivers of ice that flow downslope under their own weight which is driven by gravity. 2. The basal layer of liquid water also helps the glaciers slide along underlying bedrock. The basal layer acts like a lubricant when the liquid water when it melts under the weight of the ice, the ice then uses the liquid water to slide down the slope. -------------- MOVEMENT: Why do Alpine glaciers on the west side of the Sierra extended farther downslope? 1. higher precipitation relative to the much drier eastern slopes. 2. regional tempetures 3. global temperatures -------------- Glaciers and Debri: Debri from surrounding mountains tend to line the margins of the glaiers. The piles of debris are evident when two glaciers converge, the lines of debris merge, forming a single linear strip of dark rock along the boundary between the two conjoined glaciers. The loose rock then gets carried along on the surface of the ice. These alpines also bulldoze any sedminets or rocks in front of them. ------------ the erosional effects of Ice Age glaciers are the most important factor in the formation of landscapes national parks.

extensional faulting

An extensional fault is a fault caused by stretching of the Earth's crust. Stretching reduces the thickness and horizontally extends portions of the crust and/or lithosphere. In most cases such a fault is also a normal fault ....but may create a shallower dip usually associated with a thrust fault. This type of faulting is also responsible

oldest rocks in Death Valley?

Are Precambrian metamorphic gneiss rocks. They are found along the faulted edge of the Black Mountains.

The salt pan in Death Valley is characterized by large polygonal (often six sided) cracks in evaporite deposits. These deposits:

Are found in the Badwater Basin, these polygonal cracks are the products of flash floods. When flash floods descend from the mountain ranged the carry a variety of sediments; sand, mud and even Boulders. Larger sediments are left behind at the edge of the basin while smaller sediments are deposited at the center. Scorching temperatures then bake the muds and as the clay minerals lose water they form a polygon shaped plates. From the cracks, evaporation causes the precipitation of salt crystals that then ooze from the cracks. ——————————————————————- - Most of the Bandwater basin is covered by a salt pan- a white expansion composed of salts History: During wet years, precipitation of the ephemeral lakes that once filled the enclosed basins were outpaced by evaporation and the arid climate of DV leaving behind these salt flats Process: since the basins are enclosed the slat does not run off the mountain ranges and into the sea Source of salts: the drainage systems that feed into the valley help maintain theses salt pans - minerals that drain into the flats are quickly evaporated and dissolved until salt is the only mineral the remains

Exfoliation/onion skin jointing in the Sierran national parks:

As more and more of the overlying rock is eroded, the body of granite tends to expand and crack as successive sheets, creating the onion-skin outer surface.

Alluvial fans on the base of the Black Mountians

Aside from fault block and mountain ranges alluvial fans are also key characteristic of DV Steep reliefs and normal faulting produce this relief/alluvial fan Environment: arid, little rain, flash floods Process: when sediment deposits (a mix of cobbles, large boulders, sand and mud) spread from the mouth of the canyon they are pushed through and out of the mountain range- think of a smoothie spilling from table to floor. These fans are destructive and dangerous since flash floods during storms can carry away these sediments

How do convergent margins occur in the Rocky Mountain?

Because it is mission volcanic rock: 1. it is likely that the shallow subduction increased the rate of plate convergence or the subduction thickened oceanic crust + 2. which then caused the subducted slab turned off volcanism and the lithosphere no longer plunged deep enough to heat up and drive off fluids to reduce the mantle melting temperature. = 3. This caused shallow angle subduction to produce a broad belt of mountains. ----------- History: 1. it lies farther from the coast 2. it is missing late Mesozoic/early Cenozoic aged volcanic rocks, indicative of a volcanic arc (like the\hvolcanic arc\hof the Andes). (volcanic arc: built by fluid-flux melting is a feature of subduction zones)

How do batholith (mezazoic) form in the Sierra Nevada? (Ancestral Sierra Nevada )

By the hundred or more plutons that overlap with one another and collectively form a larger mass of granitic rock called a batholith. The granitic rock of the Sierran batholith forms the greatest mass of the Sierra Nevada and comprises the highest peaks of the range.

Ventifacts are common in Death Valley. These features:

C. have polished or grooved surfaces from blasting by sand grains ventifacts are created by the sandblasting effects of winds that carry airborne sand particles. The pressure of the winds polish down the surface of the rocks.

Which of the following statements is false regarding features and processes of national parks in the Sierra Nevada?

E: The rocks that you hike on in Sequoia/Kings Canyon NPs were intruded at roughly the same time they were uplifted into today's Sierra Nevada True:

Sierra Nevada Elevation

Elevation: It extends NW and SE 600 KM The highest elevations from range extend from N. Yosemite to S. Mount Whitney being the highest (located in sequoia national park) coast rages are to the W of the MSN

The present flat surface that visitors walk on in Yosemite Valley is comprised of the same granite as the surrounding cliffs.

False

At the surface, the basins and ranges are composed of the same rock type.

False. Base is Precambrian metamorphic gneiss and is separated by a 2.7 b.y an unconformity upper layer Paleozoic sedimentary rock that dates 500 m.y and is exposed on the western slope Basins are corespondents of down dropped fault block. These faults are identifiable by the thick sediment wedges that are divided from the surrounding ranges.

(Rocky Mountains) Faults develop under compressional, tensional, and shear stress and represent a planar break n the Earth across which there is motion. For instance:

Faults are classified on the motion of one block relative to the other. 1. 2. 3.

Ductile Deformation/ Folding= anticlines and synclines (Rocky Mountains)

Folds form in two main geometries and often occur together in compressive tectonic environments like Glacier National Park: 1. Anticlines are upward arching folds with older rocks in the middle (the core of the fold) 2. synclines are downward arching folds with younger rocks in the middle ( or core of the fold)..

Rock Fall Yosemite national park video:

Forces shaping Glacier Point: Rock fall has been major in shaping Glacier point. GP is an eroding cliff that overlooks Yosemite Valley. ---- Were impacted and shaped by rockfalls as well: 1. El Capitan 2. Half Dome 3. forest at talus slopes --------- Yosemite valley is a glacially carved canyon. --------- Historical evidence of rockfalls: Boulders are evidence that rockfalls have been happening for thousands of years IDENTIFYING OLD ROCKFALLS: old rockfall boulders are covered in lichen and moss. They are not a fresh boulders. ------------- Devices used to predict rockfalls: 1. laser scanning, 2. computer modeling, 3. monitoring of the cliffs.

Brittle vs. Ductile Deformation (Rocky Mountains)

Higher temperatures and pressures rocks respond to stresses by: 1. Ductile deformation which means they flow as a weak solid and fold - meaning they deform without breaks, like putty ----------------------------------------- In lower temperatures, depth and pressures rocks respond through the process called: 2. Brittle Deformation: become brittle and respond to stresses by faulting/ fracturing.

Faulting in the Sierra Nevada:

In the steep eastern escarpment or the upthrown side of the fault (which continues to rise) of the Sierra Nevada, is a fault zone, that lies along the base. The fault is obscured by sediment that has accumulated at the base of these mountains. The downthrown side of the fault system/displaced block is Owens Valley. ----------- The eastern landscape along the fault drops down and tilts the westward with every earthquake. The tilting gives the mountain ranges its asymmetrical shape. these mountains are called tilted fault blocks, a style of uplifting. However, the block that makes up the Sierra is moved upward along the fault. Modern vs Ancient Sierra was only uplifted 5 m.y ago and continues to rise. -------------- sub-parallel fault lines: normal faults aren't individual they work as a system interconnected by a series of fault planes/faults ea. fault is seismically active and hence experiences and has experienced earthquakes for over a million years -------------- Faulting: the normal fault block runs on the eastern escarpment. The Sierra Nevada fault block is asymmetrically shaped into a wedge. Process: Thousands of earthquakes occurring along an extensive faulting system @ the base of the eastern escarpment once uplifted to its current elevation. Faults are defined as planar fractures within rocks where displacement has already occurred. normal faulting when fault rupturing occurs during an earthquake, rock on the opposite side of the fault will move away from it. Process: it normally occurs when tectonically induced stress inside the crust of the earth is extensional- the stress/force is basically stretching the crust. During this process, the left block is uplifted while the right block slips downward. The uplifted block then becomes exposed to weathering and erosion. Since the block is now uplifted, the weathering will erode course sedminets downslope and into the shallow basin that overlooks the displaced/offset block that slipped downward. Overtime the down block will be filled to the surface level. ----------- Thinking of fault planes in three dimensions: 1. in crossection the fault plane curves down into the crust 2. where the plane intersects the surface there will be a fault line 3. fault plan also extends back into the outcrop

The Cascadia convergent margin of the Pacific Northwest (Ancestral Sierra Nevada )

Is an active and modern volcanic continental arc. Formed by magma that is generated along the interface between the subducting plate and over-riding plate.

Jointing in the Sierran national parks:

JOINTING occurs in response to stresses imposed on the rock during the uplift of the Sierran tilted fault block (mountain building. Or the relief of pressure as glaciers melted on both sides of the crest (frost wedging) Jointing occurs vertically and at an inclined angle (@ slope) like the Three Brothers in YNP In Kings Canyon NP weathering and erosion along joint planes are responsible for massive vertical slabs of rock in the outcrop. ------------------- JOINT CRACKING: Joints are planar cracks within a mass of rock that typically form as sets of sub-parallel fractures. They permit the infiltration of water into the body of the rock, enhancing the weathering and disintegration of the rock. JOINT CRACKING ELEMENTS 1. Tree roots physically pry apart the rock along the joint plane. 2. joints excavated by the frost wedging of water that freezes at night or winter. Expanding ice then wedges apart the rock on either side of the joint plane. ------- DOME JOINTING (are granites): formed by a type of jointing called exfoliation/ "onion-skin jointing.". The separation between the rocks is the actual jointing visual image: vertical jointing looks like messy stacked books or layers on top of layers hence the onion skin analogy. The layers slide off as a rockfall, like stacked books falling. --------- DOME JOINTING/Exfoliation/onion skin jointing: 1. Confined rocks/plutons that are uplifted/exposed within growing mountains (mountain building) are reduced in pressure. The granite/pluton then relaxes (breaking apart into exfoliation jointing) due to erosion and expands outward and upward. 2. At some point, the outer expanding zone exceeds the strength of the rock, allowing the outer veneer to separate along an arcuate crack. 3. As more and more of the overlying rock is eroded, the body of granite tends to expand and crack as successive sheets, creating the onion-skin outer surface.

Key Features of Mt. Whitney in Sequoia National Park:

MOUNTAIN PEAKS: Mt. Whitneys peak forms the highest peak in the contiguous 48 states. The granitic rock of the Sierran batholith forms the highest peaks of the range. Mt. Whitney landscapes were carved by Ice Age alpine glaciers.

All of the following are tilted fault block mountain ranges except:

Montana Rockies

How rocks deform and change during mountain building?

Mountain building or "orogeny" involves rock deformation in response to: 1. tectonic forces 2. metamorphism 3. magmatism in response to the increased temperature and pressure of rock burial.

What type of faults is the Death Valley floor underlined by?

Normal and strike faulting. These faults are and additional component of extension across Death Valley that result in the basins dropping below sea level. note: Relief or topographic relief describes the amount of topographic change within a particular area.

Granite Yosemite national park video:

Parks/Features Granite: 1. Olmsted Point 2. Half Dome 3. El Capitan --------- Process: Once derived from a magma chamber granite first cooled slowly beneath the surface of the earth. Over thousands of years this process formed large crystals and filled most of the cracks of the rock with magma, while at the same time Strengthing it. ------------- Strength and Glaciers: due to its strength glacier had a difficult time transporting and eroding through the rock.

Rockfalls in in the Sierran national parks:

Rockfalls (most prevalent in SN): joint planes penetrating all the way through the body of the rock, weaken the rock faces along the vertical joints and create a gigantic vertical slab, that breaks away and crashes down as a rockfall (the rapid movement of rock and soil) ROCK FALLS FROM VERTICAL JOINTING look like messy stacked books or layers on top of layers hence the onion skin analogy. The layers slide off as a rockfall, like stacked books falling. WHAT TRIGGERS ROCKFALLS? 1. intense rainfall, 2. earthquakes 3. weathering and breakdown of the rock. Yosemite and the other Sierran parks are prone to rockfalls because of the homogenous granitic rock and the pervasive vertical fractures and exfoliation surfaces that separate slabs of rock from the parent body. EVIDENCE: Evidence for the occurrence of past rockfalls is revealed by the huge piles of angular blocks of talus rock that line the base of many cliffs in Yosemite and the other parks.

Key Features of Glacier Point in Yosemite National Park

Rocks: 1. Igneous rock, granite formed during the Mesozoic era. The strength of the rock has slowed down the process of weathering and erosion of the landscape- unlike volcanic rock which easily disintegrates 2. Alluvium (low): loose sand and gravel found in stream valleys. It barely covers the granitic rock beneath. 3. Original country-rock: "older metamorphic rock" that the various magma chambers intruded into back in the Mesozoic. ------------ landforms: Domes: Home unique landform like the Half Dome. Cause Dome is composed of strong and weather-resistant granite, previous glaciers were unable to fully weather down the rock, giving it the half-dome shape. hanging cliffs: The waterfalls of Yosemite and the other Sierran parks all originate from hanging valleys, with Bridalveil Fall ------------- Rock formation features: jointing: there two main orientations of joint sets that occur at right angles to one another: one set trending northeast and another trending northwest. erosion: hanging valleys, U-shape valleys

Sierra Nevadas rock origin (Sierran Granite )

Rocks: igneous rock, granite formed during the Mesozoic era. The strength of the rock has slowed down the process of weathering and erosion of the landscape- unlike volcanic rock which easily disintegrates BATHOLITH GRANIT: Formed by plutons that overlap with one another and collectively form a larger mass of granitic rock called a batholith. ----------------- process: solidified from molten magma deep beneath surface during Mezisoic era. hence rocks are the remains of magma that erupted from magma chambers. hence the rocks comprising the land are older than the landscape itself. Rocks that form by crystallization from a molten magma or lava are called igneous Solidification of igneous rocks: 1. may occur either inside the earth in a magma chamber 2. or on the surface of the earth along the flanks of a volcano.

Curry Village lies outside the flood hazard zone, but inside the rockfall hazard zone.

TRUE, cause the October 2008, rockslide affected the Curry Village park area

The peaks in the Grand Teton National Park are the result of very large displacement (30,000') on a normal fault. The amount of displacement can be determined by:

Teton NP is a basin and range type of tilted fault block mountain range imposed on the margin of the Rocky Mountains. It's primary feature is the active Trenton fault. The scarp fault, marked by the planar surface of the fault Most abundant rock is metamorphic gneiss- original date of metamorphism is 2.7 b.y, which occurred during the Precambrian phase of mountain building During this phase older rocks were intruded (intrusion) by granite and magma and pushed into cracks deep under ground Intrusion is evident at the peak of mount Moran by the vertical bands of geniss (dikes) compromised by solidified black magma (Diabase, its a volcanic rock) that cut the country rocks Base is Precambrian metamorphic gneiss and is separated by a 2.7 b.y unconformity upper layer Paleozoic sedimentary rock that dates 500 m.y and is exposed on the western slope Mountain building phase is marked by extensional faulting during the late Cenozoic era that pulled apart the underlying crust and resulted in normal faulting which produced fault block mountains. The normal fault in NP is responsible for the controlling uplift in the park. During a series of episodic earthquakes the fault ruptured and cause the mountain block to rise upward while the Jackson hole dropped downward Four main elements of NP landscape are: the mountains, valley, sparkling lakes, and snake rivers U-shaped valleys cut westward across the Trento mountains. These valleys, orginally v-shaped were eroded by networks of streams that drained the highlands. These streams and valleys were later modified to u-shape by alpine glaciers that transported large sedimentary debris within the ice and eroded rock material like a bulldozer as it sloped across the tentons and into the Yellowstone ice cap. However as the glacier began to melt it released debris and formed and iced toe of debri called moraine. These moraines are a marker of the glaciers downslope movement. In the long run sediments that form TERMINAL moraines grow trees. However the debri in Jackson hole is too gravely for good soil. Lakes in terenton are a product of terminal moraines. These moraines act like a dam and enable snowmelt form surrounding mountains and streams to feed the lakes. These dams also prevent flooding and trap snowmelt. The alpine glacier is are also responsible for the glacier features present in Trernton NP. Sediments filling the Jackson hole are Cenozoic sandstones, shales and conglomerates snowmelt and rain fall flow westward to the Pacific Ocean drainage

Rocky Mountains Location :

The Rocky Mountains are a chain of mountain ranges extend from: 1. northern New Mexico, 2. through Colorado, 3. Wyoming, 4. Montana 5. and northward into Canada.

The granites of the Sierra Nevada are formed by (Ancestral Sierra Nevada ):

The granites of the Sierra Nevada are the eroded remains of Mesozoic plutons that were uplifted isostatically as well as dynamically along faults. ----------------------------- INTRUSIVE DOMAIN/RELEAM: The "granites" that characterize the Sierra are formed beneath the surface in the so-called intrusive domain/realm. the intrusive domain is a process in which molten magma intrudes the country rocks that are already in place- beneath the earth ----------------- PROCESS: however, the process that forms granite itself is called plutonism. Rocks like granite are commonly known as plutonic igneous rocks. ------------------- ROCK COMPOSITION: these rocks are composed of interlocking mosaic mineral crystals. With time and cooling, perhaps over a few tens of thousands of years, the atoms eventually link up via chemical bonds, forming the orderly atomic arrangement of mineral crystals. The result is the interlocking mosaic of minerals that comprise the plutonic rock -------------------- BATHOLITH GRANITE: plutons that overlap with one another and collectively form a larger mass of granitic rock called a batholith. --------- INTRUSIVE MAGMA CHAMBERS: In the Sierra, a few hundred individual magma chambers intruded into the overlying rock of the crust where they slowly cooled to become granitic plutons. over this 80 m.y. period, some magma chambers intruded early then solidified, while others came up later, intruding into and overlapping with the older plutons.

Effects of glaciers on the landscapes of national parks of the Sierra Nevada:

The three main processes that acted collectively to create the Sierran landscapes are: 1. jointing: meltwater from the lowermost part of the glacier infiltrates into joints within the underlying bedrock where it may freeze, slowly wedging blocks of rock away from the bedrock in a process called plucking. 2. rockfalls: (most prevalent in SN): joint planes penetrating all the way through the body of the rock, weaken the rock faces along the vertical joints and create a gigantic vertical slab, that breaks away and crashes down as a rockfall (the rapid movement of rock and soil) 3. glaciation: Glaciers are essentially rivers of ice that flow downslope under their own weight which is driven by gravity. -------- How does CLIMATE impact landscape: The warm interglacial phase we live causes alpine glaciers in the Sierra to tend to be small and confined to the highest elevations of the range. ----------------------- HISTORICALLY: Visualize glacial ice in each of the valleys, separated by the linear walls of rock. the highest peak in the distance, as an island of rock, sticking up above the vast expanses of whitish-blue ice. There are only about 99 small glaciers remaining in the Sierra today.

Curry Village lies outside the flood hazard zone, but inside the rockfall hazard zone.

True

Death Valley was filled with water several times in the past few million years. Which of the following provides evidence of these lakes in the valley?

a. the presence of salt deposits in the Badwater Basin B. a series of wave cut terraces on rocks well above the valley floor such as at Shoreline Butte c. the presence of young, fine-grained sediments that accumulated in lakes —————————— 8.3 During Pleistocene ice ages, ice glaciers were a dominate feature of the Sierra Nevada mts and southern valleys; these valleys has cooler and wetter climates Hence evidence suggests that basins in DV were once sites the of lakes filled by melt water. These lakes were responsible for feeding the rivers that flowed through the lower elevated basins Lake Manley, was lake in DV that was fed by the lakes in Panamint Valley Topographic features: series of horizontal lines carved into the flanks of hills. Lines are the result of wind driven waves that marked nearby rocks over an extended period of time- also know as wave-cuts. These lines also serve to as marker to identify the depth of theses lakes. Wet lands are spring fed pond are also indicative of wet environments- underground aquifers heed theses waters —————————————————- By late Precambrian the earlier mountains were eroded to down to sea level. Around 850 million years ago throughly the Paleozoic and Mesozoic there were rising and falling seas. These seas would deposit carbonate sediments. The sediments are visible throughout the Mosaic canyon. Since these seas were near the equator the water was warm. Process is similar to that of the Grand Canyon

Matthes Crest in Tuolumne Meadows, Yosemite, is a narrow, steep-sided ridge formed by glaciation on two sides. Such a glacially-eroded ridge is called

an arete

What geologic setting is responsible for the formation of the rocks exposed in the Sierra Nevada and adjacent features?

an ocean-continent convergent zone

You know that flash floods transport eroded debris like cobbles, pebbles, sand and silt onto alluvial fans. If through time the alluvial fan gets buried, which of the following sedimentary rocks do you think might form?

conglomerate

Ductile deformation (folds)

deforms without breaks, like putty

What geologic process/feature was most dominant in creating the rounded domal shape of the intact part of Half Dome in Yosemite National Park?

exfoliation

The modern Sierra Nevada was uplifted during this event.

extensional tectonics relatively late in the Cenozoic

What is a primary reason an increase in glaciers on land would cause sea level to fall?

glaciers tie up large volumes of water that would otherwise be in the sea

ranges?

groups of mountains, created by upper faulting in the brittle part of the crust

Ventifacts are common in Death Valley. These features:

have polished or grooved surfaces from blasting by sand grains

Isostatic rebound/isostatic uplift of mountains in the Ancestral Sierra Nevada:

is a slow process of Earths crust rising as the result of the removal of mass from the crust. 1. in the Ancestral Sierra, Nevada erosion caused the slow isostatic uplift of mountains while at the same time it removes the rock from the highest elevations. 2. the mountains are diminished and the thick crustal root gradually rises, exposing the deeply buried granite plutons at the surface The last step in the uplift of the Sierran batholith began about 5 m.y. ago as the modern Sierra Nevada began to rise as a tilted fault block mountain range. 3. granitic plutons were uplifted to their current heights of up to 14,000' in the High Sierra. However, the normal faults in the east side of the range (in the Mono Basin) ruptured it into countless series of earthquakes. 4. afterward a network of rivers was established that drained the gentle western slopes and transported its sediments and water to the Central Valley. Note: mountains can slowly rise in response to the erosional loss of mass at the highest elevations of the range. ---------------

Topographic feature of Modern Sierra Nevada (6:1)

landscape: 1. Gentle western slopes: because these slopes catch most of the moisture from storms coming off the pacific, they have more vegetation. slopes are also surrounded by draining rivers like the Merced, Cosumnes, Yuba, Feather, and American that drain into the SJQ river. 2. Steep escarpments (slopes): on the eastern side are dryer than on the west. These steep slopes have been modified by erosion. Two main rivers: san Joaquin and Sac river flow through the central valley and meet @ the CA Delta estuary. 3. Broad foothill belt: 4. Vertical cliffs: El Capitan -------- Parks within SN: Yosemite is in the central part of the SN. granite dominated. Sequoia NP also has a dominance of granitic rock like the Sierran batholith Kings Canyon is in the southern sierra, in the Sierran batholith ------ Rocks: 1. Granite: YNP and SN are massive Granite dominated 2. BATHOLITH GRANITE: plutons that overlap with one another and collectively form a larger mass of granitic rock called a batholith. Granite formed as molten rock deep in the earth and then crystallized and brought upward through uplift and tiling. once exposed, water and glaciers weathered down rock and shaped the current landscape. ------------ Faulting: the eastern landscape along the fault drops down and tilts westward with every earthquake. The tilting gives the mountain ranges its asymmetrical shape. these mountains are called tilted fault blocks, a style of uplifting. However, the block that makes up the Sierra is moved upward along the fault. Modern vs Ancient Sierra was only uplifted 5 m.y ago and continues to rise.

Basins?

low areas of land, often surrounded by mountains

During what time did the western U.S. experience a large amount of crustal extension?

middle and late Cenozoic

One or both sides of a basin in the Basin and Range province is likely bounded by a ________ fault

normal

normal fault/hanging wall

normal fault/dip-slip: break in rock caused by tension forces, where rock above the fault surface moves down/is lengthened relative to the rock below the fault surface This occurs in tensional tectonic environments.

The remaining glaciers in Yosemite National Park are most likely to be found

on north facing slopes, only at the highest elevations

Broad, white expanses of evaporite salts are characteristic of which of the following physiographic features of deserts like Death Valley?

playa lakebeds

The Basin and Range province includes much of the western US, extending from Oregon into northern Mexico. The Basin and Range:

reflects substantial extension following the birth of the San Andreas

The rocks exposed in Yosemite National Park are predominantly granitic igneous rocks that are part of the Sierra Nevada batholith. These igneous rocks:

represent the product of a long period of subduction along the west coast, have been subject to glacial erosion over the past 2 million years

What is the topography of DV?

sand dunes, are the product of eroded rocks from surrounding mountain ranges that have been broken down into sand particles/sediments. Rocks deposited by flash floods often grind against each other, breaking down to smaller sediments. Winds also carry sand grains across the dunes, dropping them back into the ground and the blowing them into the air. ventifacts are created by the sandblasting effects of winds that carry airborne sand particles. The pressure of the winds polish down the surface of the rocks. Sliding stones of racetrack playa is a dry lake composed of slit and clay. The mud cracks on the lake a produced by a repeating cycle of wetting and drying. The stone originally tumbled from the rocky ridges if the limestone at the southern playa. alluvial fans when sediment deposits (a mix of cobbles, large boulders, sand and mud) spread from the mouth of the canyon they are pushed through and out of the mountain range- think of a smoothie spilling from table to floor. salt pan/flats since the basins are enclosed the slat does not run off the mountain ranges and into the sea Source of salts: the drainage systems that feed into the valley help maintain theses salt pans minerals that drain into the flats are quickly evaporated and dissolved until salt is the only mineral the remains basins low areas of land, often surrounded by mountains ranges groups of mountains, created by upper faulting in the brittle part of the crust

The large crystals of the granitic rocks of Yosemite are ideal for rock climbing. They formed as a result of:

slow cooling within a magma chamber beneath the surface

Melting due to water driven off of the Farallon plate produced magma that buoyantly rose upward during this event, forming the ancestral Sierra Nevada.

subduction along the western boundary of North America during the Mesozoic

Death Valley National Park contains peaks higher than 3300m (Telescope Peak) in close proximity to areas below sea level (e.g., Badwater). This large difference in elevation is primarily due to:

subsidence from both Basin and Range extension and normal faulting

Landscapes in Yosemite National Park have been significantly modified by glaciation. Most glacial erosion occurs by glacial plucking or quarrying:

that most efficiently removes rock that is already fractured, that occurs when water produced at the base of the glacier seeps into fractures and then refreezes, that can dislodge large blocks that can be transported by the glacier

The peaks in the Grand Teton National Park are the result of very large displacement (30,000') on a normal fault. The amount of displacement can be determined by:

the elevation difference of a sedimentary layer on either side of the fault

What does the San Andreas fault mark?

the fault is indicative of horizontal sliding plates, across what is a considered a vertical fault SA is a strike slip fault, Transform boundary The pacific plate is on the west side of the fault. This fault moves north

Death Valley was filled with water several times in the past few million years. Which of the following provides evidence of these lakes in the valley?

the presence of salt deposits in the Badwater Basin a series of wave cut terraces on rocks well above the valley floor such as at Shoreline Butte the presence of young, fine-grained sediments that accumulated in lakes