BYU GEO 101 Exam 2

What is weathering?
The breakdown of rock by physical and chemical reactions with air and water.
How do smooth rocks get cracks?
-Naturally occuring from the expanding and contracting from the cooling process
-Earthquakes
-Lava – as it cools, it contracts, causing cracks
These affect the type and rate of weathering.
Climate and rock type
Rock breaks down faster in this type of climate.
Hot, moist climates
Joints in rocks
Fractures. Results from tectonic stresses of contracting to to cooling igneous rock.
Three types of tectonic stress
Compressive
Tensional
Shear
How is columnar basalt formed?
When the lava cools, in contracts towards a center point, creating a 5 or 6 sided column.
What is physical weathering?
The mechanical fragmentation of rocks from stress.
What are some types of physical weathering?
-Frost wedging
-Thermal weathering
-Wetting drying (hydration)
-Unloading (exfoliation)
-Salt wedging
-Biological weathering
Frost wedging
when water gets into a crack, and the freezes, expanding the crack
Thermal weathering
The weather changes from hot to cold
Wetting drying (hydration)
Absorption of moisture causes swelling.
Unloading (exfoliating)
Expanding after heavy loads are removed, or the expanding removes some rock.
Salt Wedging
Water settles into the cracks, evaopartes, but leaves the salt behind. Salt crystals grow and shatter the fence post.
Biological weathering
Plant roots can expand cracks.
Burrowing animals carrying air and water down into bedrock.
What is chemical weathering?
Chemical reactions with minerals that break down rock.
Three types of chemical weathering
-Hydrolysis
-Oxidation
-Dissolution
What is hydrolysis?
A chemical reaction between water and another substance to produce a new compound that is usually weaker than the original
What is oxidation?
When oxygen dissolved in water comes into contact with certain rock minerals.
What is dissolution?
The process by which a solid, liquid or gas forms a solution in a solvent
What is a karst?
Chemical weathering where limestone bedrock dissolves when it comes in contact with groundwater.
What landforms produced from the karst process?
-Sinkholes
-speleothem (the caves)
-haystack hills
-tufa cones
What is a speleotherm?
A cave created thru the karst process. Contains stalactites and stalagmites.
How are haystack hills formed.
Over time, sink holes from the karsting process merge together. the ground left behind are known as haystack hills.
Name some hydrothermal features.
Geysers
Hot springs
Fumaroles
Tufa cones
What are geysers?
Where groundwater comes in contact with heated igneous rock below the surface. As the water heats, the pressure builds until it blows.
What are hot springs?
Where ground water comes in contact with heated igneous rock, but it is not under pressure.
What are fumaroles?
Like a geyser, but instead of water, it is just steam.
What are tufa cones?
The result of overflow of warm groundwater. Midway at the Homestead.
What is mass wasting?
The down slope movement of earth material due to gravity.
How does water affect mass wasting?
Water lubricates, makes everything slippery and adds weight. It saturates the soils.
Most important factors in slope failure

Saturation of slope material with water

 Earthquakes

 Freezing and thawing

Types of slope failure
Rockfall
Slump
Earth or mudflow
Solifluction
Creep
Describe rockfall
Cracks in rocks indicate water erosion. Rockfall can be one rock, or lots. Accumulated rocks and the bottom of a cliff is called Talus.
Describe slump
It creates step-like terraces as it slumps down.
Describe earth or mud flow.
Lots of water, like a muddy river. Very moist environment
Describe solifluction.
Occurs in extremely cold environment, high altitude, in permafrost. The top few inches or feet thaws and starts to slide over the frozen layer. Creates irregular terrain.
What is Pangaea?
The supercontinent that was made up of all landmasses on the earth
What is Laurasia?
The north portion of the supercontinent Pangaea.
What is Gondwana?
The southern portion of the supercontinent Pangaea.
Describe Continental Drift.
Alfred Wegner’s theory that the continents were drifting across the ocean bed. He recognized the puzzle-like shape of the continents and the plant, wildlife and rock that matched on continents separated by ocean. Unfortunately, he did nt know the mechanism behind the theory and so it was dismissed.
Describe Plate Tectonics.
The lithosphere is made up of large plates that shift and move as a result of convection. Plates were dicovered through seafloor mapping and mapping of earthquake patterns.
Seafloor spreading
Discovered thru Paleomagnetism and Ocean Rock Floor Sampling
What is a Hot Spot?
A spot deep in the mantle which leaks hot magma/lava to the the earth’s surface. Hot spots do not move. The Hawaiian islands were created by hot spots. Yellowstone has one.
What is an accreted terrane?
The addition of material to a plate during the subduction process. Accounts for geologic incongruities between continental interiors. NV, OR, WA all accreted onto the North American Plate.
What is Diastrophism?
Deformation of the earth’s crust, particularly thru folding and faulting
Describe earths folding.
It is the result of compressional forces. Downfold is a syncline, upfold is anticline, monocline does not fold.
Anticlinal Valley
Where the layers of bedrock erode quickly because of folding and looks like a syncline, but is not.
Describe faulting.
Rock that has been forcefully broken. Occurs along zones of weakness in the earth’s crust. Common in Coastal areas
Shield volcano
Broad domes. Wider than it is tall.
Magma is extremly hot and very runny. Gas bubbles rise to the top and are released into the atmosphere. Found over hot spots. Hawaii.
Composite or strato volcano
Magma is cooler, thick, pasty and viscous. Bubbles cannot rise so the pressure builds until there is a large explosion. Cone shaped. Mt Pinatubo
Name some extrusive volcanic landforms.
Shield or composite volcanoes, and caldera.
Name some intrusive volcanis landforms.
Batholith
Laccolith
Dike
What is a batholith?
Magma that cools and solidifies below earths surface. Igneous Intrusive. Usually Granite.
What is a laccolith?
Magma that gathered in one spot between two sheets of sediment. Pushes the upper layer upward.
What is a dike?
A vertical layer of magma that melted its way up.
Wegner’s evidences for continental drift.

-Puzzle-like fit of widely separated continents

-Similarity of rock and mountain formations near coastlines of separated continents

-Matching fossils of extinct species on widely separated landmasses

Three types of plate boundaries.
Divergent
Convergent
Transform
Describe a divergent plate boundary.

Where the boundaries are being pushed apart. This happens at ocean ridges, were the convection process pushes magma up and pushes the boundaries apart.

Mid-Atlantic Ridge

Describe a convergent plate boundary.

Where plates come together. Oceanic plates collide, denser one gets drawn down. Friction causes magma to move up. Unsubducted plate will have island chain. Aleutian Islands. 

Oceanic-Continental – Oceanic is more dense, so it will subduct and create a volcanically active mountain range. Cascade Mtn Range.

Continental-Continental – They don’t subduct, so they move up, creating mountains. Himalayan Mountains.

Describe a transform plate boundary.
The plate are sliding past eachother. San Andreas Fault.
Example of landforms assciated with faulting.

Block Mountain Range – the Wasatch Range.

Horsts and Graben – Great Rift Valley in Africa

Stream Discharge
The volume rate of water flow. Amazon has greatest discharge.
Tributary
A small stream that jons another. Small streams have no tributary.
First stream orders are without tributaris. When two first-order dtreams combine, they are called a 2nd order stream.Eighty percent of streams are 1st, 2nd, or 3rd order.
Channel
The trough water travels in.
Fluvial transportation
All streams transport sediment. Stream-transported sediments are eventually deposited in a river or ocean.
Types of fluvial transportation
Dissolved load – salt/minerals
Suspended load – clay and silt
Bedload – sand and larger
Characteristics of bedload
Carries partciles the size of sand or larger.
Saltation is the bouncing of sand as it goes down the stream
Traction is the process of pushing larger rocks down the stream
If a stream doubles in speed it can carry rocks 64x heavier.
Name four channel patterns.
Straight
Meandering
Sinuous
Braided
Describe how a delta is formed.
As streams dump into the cean, they deposit sediment in theo the sea until the sediment builds up and blocks the stream, rerouting the water. Mississippi River.
Describe a floodplain
Flat or nearly flat plain adjacent a river. Extends to edges of valley, created by meandering. Floods when river is full.
What is a levee?
A natural or artificial earthen ridge that runs parallel to a river to prevent overflow.
Effect of stream gradient.
Higher gradient (steeper) river flow faster, can carry more stuff.
What is a Yazoo stream?
A small tributary that runs paralle to a larger stream. Will Usually join the larger one. When levees form, it has a harder time eroding through.
What is a distributary?
A stream that branches off from the main channel. Usually occurs near an cean or lake.
What is an oxbow lake?
A cutoff meander. The water ct through the rock, leaving a u-shaped river.
What is alluvium?
Sediment deposited by a stream.
What is a canyon?
A ravine between cliffs carved by water.
What is a bluff?
A cliff near a river which has not been eroded yet.
Erosional landform
Where will you find a sand bar or point bar? How is it created?
On the inside of a meandering stream.The water inside the curve is mving slower, so it deposits some of its sedimentry content.
The difference between perennial and ephemeral streams.
Ephemeral streams are occaisional, they don’t flow all year. Perennial streams run al year.
Erosional and depositional dynamics of river meanders.
As meanders curve, they erode the outer edges and deposit on the inner edges.
What are paired terraces?
Terrace at opposite sides of a river that match in height. Reflects where the river bed was before it cut down into the earth. Erosional.
What is an entrenched meander?
The same as incised. It cuts down into the earth.
Describe a knickpoint retreat.
The river bed is resistant to erosion, be the earth underneath that layer is not. At water falls, the water erodes the less resistant layer, causing the bed layer to fall because it has no support. Niagara Fals used to retreat 3 feet per year. Now it is closer three inches every decade. They rerouted the water for energy.
Subduction zone island chains
Oceanic subducting: Aleutian Islands

Leave a Reply

Your email address will not be published. Required fields are marked *