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Physical Geography Exam I > Exam IV > Flashcards

Exam IV Flashcards

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1
Q

Who was Alfred Wegener?

A

German geophysicist and meteorologist son in law of climatologist Koppen.

He revived the theory of continental drift and thought there was a supercontinent called Pangea

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2
Q

What was Alfred’s evidence for continental drift?

A
  1. Continental margins of Africa and South America fit together like puzzle pieces
  2. Both sides of the Atlantic Ocean have distributions (like coal rock) one either side as if they are continuous
  3. Life specific to an area appeared on either side of continents and would have been much too heavy to be carried by wind
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3
Q

Why was Alfred’s theory rejected?

A

For two main reasons:

  1. Earth’s crust was thought to be too rigid to permit such large scale motions (how could solid rock plow through solid rock?)
  2. Wegener did not provide a suitable mechanism for all this to happen
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4
Q

What is the current evidence for the scientific theory of plate tectonics?

A
  1. Midocean ridges
  2. Paleomagnetism
  3. Seafloor spreading
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5
Q

What are mid-ocean ridges?

A

40 thousand mile interconnected chain of ridges under the ocean

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6
Q

What is paleomagnetism?

A

When any rock that contains iron forms it gets magnetized so that it is aligned with Earth’s magnetic field - studying this shows the permanent record of the earth’s magnetic field at the time the rock solidified.

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7
Q

What is seafloor spreading?

A

Theory that says mid ocean ridges are formed by currents of magma rising up form the mantle and volcanic eruptions create new ocean rock that spread laterally away from the ridge.

Takeaway is that mid ocean ridges contain the newest crust, whereas the further you move away from the ridges toward the continents you get older crust.

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8
Q

What are divergent boundaries?

A

When magma from the asthenosphere rises up between two plates which then produces a line of volcanic vents that spill out basaltic lava onto the ocean floor

Examples include mid ocean ridges and continental rift valleys

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9
Q

What are transform boundaries?

A

When two plates slip past each other in a lateral fashion.

When they snag they build up energy until a sudden slip causes a release of energy and causes usually shallow EQs

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10
Q

What are convergent boundaries?

A

When plates collide and are often called destructive boundaries.

Three types:
Oceanic-Continental
Oceanic-Oceanic
Continental- continental

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11
Q

What is an example of a oceanic-continental boundary?

A

Andes in South America

Cascades in NorthWest America

They often form chains of volcanoes.

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12
Q

Explain the basics of oceanic-oceanic plate boundaries.

A

When two oceanic plates collide, subduction occurs, forming an oceanic trench.

Here shallow, intermediate and deep focus earthquakes occur, and volcanoes can occur on the ocean floor.

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13
Q

Explain the basics of continental-continental plate boundaries.

A

Because continental crust is too buoyant to subduct the plates collide and form huge mountain ranges.

A good example of this is the Himalayas.

Volcanoes are rare, but shallow focus earthquakes are common.

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14
Q

Where is the pacific ring of fire?

A

The Pacific Ring of Fire is a horseshoe-shaped zone around the Pacific Ocean characterized by a high degree of tectonic activity, including earthquakes, volcanic eruptions, and the presence of geologic faults.

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15
Q

What is the significance of the Pacific ring of fire in creating landforms?

A

This region is significant in creating landforms due to its dynamic geological processes.

The collision and subduction of these plates result in the formation of various landforms such as volcanoes, mountain ranges, trenches, and island arcs.

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16
Q

What are hot spots?

A

Places on earth where magma rising from the mantle comes to the surface at locations that are not near a plate boundary.

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17
Q

What can happen around a hotspot?

A

Magma rises from deep within the Earth’s mantle, creating volcanic eruptions that form chains of volcanic islands or seamounts.

Over time, as the plate moves away from the hot spot, the volcanic activity ceases, creating a new chain of volcanic islands or seamounts in its wake.

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18
Q

What is an accreted terrane?

A

They are blocks of continental fragments and oceanic islands that have collided with a continent at a convergent plate boundary and are now permanently attached

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19
Q

Where are volcanoes distributed on the earth’s surface?

A

They are mainly found near plate boundaries and hot spots.

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20
Q

Why do volcanoes appear at plate boundaries and hot spots?

A

Volcanoes appear at plate boundaries due to the dynamic interactions between tectonic plates, such as subduction or divergence, which create conditions conducive to magma formation and eruption.

Hotspots, on the other hand, are stationary sources of magma within the mantle, which can generate volcanic activity regardless of the presence of plate boundaries.

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21
Q

What does volcanic activity depend on?

A

The chemistry of the magma

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22
Q

Describe the Mafic magma type.

A
  1. lower in silica content making it much more dense, and higher in things like magnesium and iron
  2. common rocks include gabbro and basalt, typical of the ocean crust

*Mafic magmas are less viscous and flow more evenly meaning it is less explosive

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23
Q

Describe the Felsic magma type.

A
  1. It is rich in feldspar and silica making it have a lower density (Silicate material are 95% of the crust)

2.The most common fesic rock is granite which is typical of the earth’s crust

  • This type of magma clogs the volcanic neck and produces violent eruptions
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24
Q

What type of magma is responsible for black beaches?

A

low silica magma that flows easily and is fast cooling

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25
Q

What type of magma is responsible for columns of brick (basalt)

A

low silica magma that takes longer to cool.

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26
Q

What is a shield volcano?

A

A shield volcano has layers of thin lava, that contains less pyroclastic material

Can be super tall but is never steep sided

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27
Q

What is a composite volcano?

A

They are volcanoes that have magma with high silica content and have alternating layers and steep slopes

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28
Q

What is a lava dome?

A

Volcano that has high silica lava that is too thick and pasty to flow very far, so it bulges up from the vent, and the dome grows

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29
Q

What are cinder cones?

A

Smallest volcanic peaks that usually contain basaltic (dense, flowing magma) that have cone shaped peaks that are built from the pyroclastic material ejected from the vent

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30
Q

What are calderas?

A

Rare occurrence when there is a collapsing inward of the volcano because of a build up of pressure

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31
Q

What are plutons?

A

Plutons are large bodies of igneous magma that cools/hardens underground, which is revealed later by erosion

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32
Q

What are intrusive igneous features and what are some examples?

A

they form when magma solidifies beneath the Earth’s surface.

examples include Batholiths Volcanic Necks, Dikes, Laccoliths Sills

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33
Q

What are Batholiths?

A

Large igneous intrusion that deforms the surface.

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34
Q

What is a dike?

A

Vertical sheet of magma crust up into pre-existing rock; erosion leaves a long narrow ridge

*result of igneous intrusion

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35
Q

What is a lahar?

A

A type of mudflow or debris flow composed of slurry of pyroclastic material, rocky debris, hot boiling water

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36
Q

What is a sill?

A

A sill is a long thin intrusive body of magma that is forced between strata

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37
Q

What is a laccolith?

A

Forms when viscous Felsic magma is forced between horizontal layers of pre-existing rock that forms a mushroom shape

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38
Q

What are some examples of extrusive igneous features?

A

Extrusive igneous features are geological formations or landforms formed by the solidification of magma that has erupted onto the Earth’s surface.

Examples include Siberian Traps Deccan Traps and the Columbian Plateau

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39
Q

What happens during folding?

A

When a colliding compressing boundary warps the sedimentary layers like the ones we see in the Appalachians

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40
Q

What is faulting and what is an example?

A

When rock structures break and one side is forcibly displaced relative to the other.

Example is that of the Sierra Nevadas

*classic fault-block mountain that was thrust upward

41
Q

What is a horst?

A

A block pushed upward (relative to the blocks on either side) by faulting.

42
Q

What is a garben?

A

A block that has been lowered relative to that of the blocks on either side due to faulting.

43
Q

What do horst/garben topography create?

A

They create many rift valleys that we see worldwide like the Rhine valley and Death valley

44
Q

Why are weathering and mass wasting considered to be the preliminaries to erosion?

A

Because they are the initial processes that break down and weaken rock and soil, making them more susceptible to being transported away by agents of erosion.

45
Q

What is denudation?

A

Generally speaking, it is the disintegration, wearing away, and the removal of rock material

46
Q

What are joints?

A

Fracture along which no movement has taken place

*there are many more joints than there are faults in the crust

47
Q

Why are rock opening so important in weathering?

A

Because weathering depends on rock opening.

Types of rock openings are joints, faults, lava vesicles and solution cavities

48
Q

What is mechanical weathering?

A

When there is physical disintegration without any chemical changes

Examples include frost wedging, salt wedging, temperature changes and exfoliation

49
Q

What is exfoliation?

A

Unloading occurs when weathering exposes rock, more surface area mean there is more opportunity

50
Q

What is chemical weathering?

A

When there is decomposition of rock material through chemical alteration.

Oxidation when O2 combines with metalic elements and minerals to form new products

Hydrolysis - when water merges chemically to form new products

51
Q

Where is weathering the deepest?

A

At or near the equator.

52
Q

What is biological weathering?

A

Could be from plants or animals.

Root takes place in rock
prarie dogs dig holes where water and gases can go down

53
Q

What is mass wasting?

A

Weathered material that is moved by gravity.

54
Q

What are some influences of mass wasting?

A
  1. The angle of repose (slope steepness)
  2. Moisture in the soil, the clay content
  3. earthquakes
55
Q

How is mass wasting classified?

A

By speed and the amount of the water.

56
Q

What is a fall?

A

Rock moving through the air via gravity

57
Q

What is a slump?

A

Rotational slip of solid mass of earth material lubricated by water.

58
Q

What is a slide?

A

A sudden detaching of rock from a steep slope that is still in contact with the slope

59
Q

What is a flow?

A

earthflow (wet, fine-grained) and mudflow (wetter, faster moving)

60
Q

What is a creep?

A

tilted fences posts or leaning headstones.

61
Q

What is solifuction?

A

caused by gradual freeze - thaw cycle on permafrost

62
Q

What is the single most important agent of landscape modification?

A

Running water

63
Q

What is the interfluve?

A

The height of land that separates adjoining valleys.

64
Q

What is the difference between a streamflow and overland flow?

A

Overland flow: the un-channelled downslope movement of surface water

Streamflow: channeled movement of water down a valley bottom

65
Q

What is a drainage basin or a watershed of a stream?

A

all the area that contributes overflow land, streamflow, and groundwater to that stream

66
Q

How are stream orders classified within a drainage basin?

A

They are classified into first-order second order and so on.

Two first order streams must meet to form a second order stream etc.

67
Q

Explain the difference in number and in length between different stream denominations.

A

Smaller streams are larger in number

Larger streams are larger in size

68
Q

Generally, what is fluvial erosion and deposition?

A
  1. Erosion is removing fragments of bedrock
  2. Deposition is transportation to another location and set them down
69
Q

What are the types of fluvial erosion?

A
  1. Erosion by overland flow - first when raindrops hit the ground it can move particles just a little, and when flow starts to form rills
  2. Erosion by streamflow - when it rains, the water runs off the land and gathers into these streams, flowing downhill towards larger bodies of water like lakes or oceans. Once it is channeled, the power of erosion increases
  3. Fluvial Deposition - Alluvium refers to the loose sediment deposited by flowing water, including sand, silt, clay, and gravel. It accumulates along the riverbed and banks, forming floodplains, deltas, and alluvial fans.
70
Q

Streams move solid material in one of several ways depending upon particle size. What are the ways?

A
  1. By solution (dissolved)
  2. Suspension (stream flow)
  3. Saltation (bouncing)
  4. Traction (pushing)
71
Q

What is alluvium?

A

deposit of clay, silt, sand, and gravel sediments left by flowing water in a river valley or delta

72
Q

What is the difference between stream competence and stream capacity?

A
  1. Stream competence - the largest particle size that is carried
  2. Stream capacity - maximum solid load that can be transported
73
Q

What is the difference between perennial and intermittent streams?

A
  1. Perennial streams - permanent flow in humid conditions
  2. Intermittent streams - streams that only occur seasonally
74
Q

What is an ephemeral stream?

A

Streams that only flow after a rain etc.

75
Q

How is stream flow measured?

A

Many stream gages are used to measure height of the stream and the velocity of the stream

76
Q

What is meant by flood recurrence interval?

A

Streamflow data gathered over many decades may provide data about the frequency and intensity of floods in the area.

The probability of a given size flood occurring in a particular year is called the recurrence interval

77
Q

How are sediments carried in channel flow?

A
  1. Some minerals are carried when they become dissolved into the water
  2. Others are carried in the suspension
  3. Bedload consists of the things that bounce off the floor called the saltatory and traction is the rolling of things on the bottom of the stream
78
Q

What are consequent and subsequent streams?

A
  1. Consequent streams are streams whose course and direction are primarily determined by the original slope and topography of the landscape.
  2. Subsequent streams are streams that develop after the initial landscape has already been formed by geological processes
79
Q

What are antecedent and superimposed streams?

A
  1. Antecedent streams are streams that existed before the current landscape features were formed.
  2. Superimposed streams are streams that develop on top of existing geological features and are not controlled by the underlying rock structure. Unlike antecedent streams, superimposed streams are formed after the landscape features have been established.
80
Q

What is the most common type of stream drainage pattern?

A

Dendritic

81
Q

What determines a drainage pattern?

A

It is shaped by the underlying surface structure

Can be dendritic or trellis

82
Q

How do floods deepen valleys?

A

Valleys deepen when a stream downcuts into the stream-bed. Includes all the things we have talked about including the power of the moving water and the movement of sediment on the bed.

Highest in areas with a steep gradient

83
Q

Why do streams meander (widen)?

A

As downcutting decreases with time, the stream begins to have segments that have little to no gradient, so the streams energy is put into meandering - laterally eroding the stream.

Mass wasting is very important in this process.

84
Q

How does meandering cause headward erosion?

A

The combination of meandering and lateral erosion gradually extends the length of the stream channel upstream, a process known as headward erosion.

As meanders migrate and widen, they erode the landscape at their upstream ends, progressively extending the stream’s course into the surrounding terrain.

85
Q

What is knick-point migration?

A

Knickpoint migration is the process by which a sharp change in slope, or knickpoint, migrates upstream over time due to erosion. It occurs when a stream or river erodes the landscape unevenly, leading to the retreat of waterfalls, rapids, or other steep sections of the channel upstream.

86
Q

What are cutoff meanders (oxbows)?

A

Cutoff meanders, also known as oxbow lakes, are crescent-shaped bodies of water formed when a meandering river or stream cuts across the narrow neck of a meander bend, creating a new, straighter channel. This process, called meander cutoff or stream avulsion, typically occurs during periods of high flow when the river’s erosional power is strongest. As the river cuts across the neck of the meander bend, it creates a new, shorter path, leaving behind the abandoned loop of the meander. Over time, sediment deposition and the growth of vegetation may separate the abandoned loop from the main channel, forming an oxbow lake. Oxbow lakes are often characterized by their curved shape and are common features in floodplain environments.

87
Q

What are natural levees?

A

Natural levees are raised landforms that parallel the banks of rivers and streams. They are formed by the deposition of coarser sediment, such as sand and gravel, during periodic flooding events. When rivers and streams overflow their banks during floods, the flow velocity decreases significantly as the water spreads out onto the floodplain. As a result, the river deposits sediment carried in suspension onto the adjacent floodplain.

88
Q

What percent of the earth’s land mass is made of deserts?

A

20%

89
Q

What makes the desert a specialized environment?

A
  1. weathering is slow because there is little water and is mostly mechanical,
  2. Soil and regolith is absent so slopes are angular etc
  3. Impermeable surfaces
  4. Sand
  5. Rainfall is limited but when it does happen it happens and water is very important in erosion in the desert
  6. Fluvial deposition is very common due to the many ephemoral streams here
  7. Wind is important but not that much
  8. There are basins of interior drainage because the water just cant reach the ocean.
  9. little vegetation
90
Q

How do humans modify rivers for flood control?

A

They build

  1. Levees
    2.Channel rivers
  2. build dams etc
91
Q

What are stream terraces?

A

Stream terraces are flat, elevated landforms found alongside river valleys, formed by the lateral erosion of rivers and deposition of sediment, often indicating former floodplain levels.

92
Q

What are entrenched meanders?

A

Entrenched meanders are tightly curved bends in a river or stream that have eroded downward into the underlying bedrock or sediment, creating steep-sided valleys or canyons.

93
Q

What are exotic streams in the desert?

A

Exotic streams in the desert are rivers or streams that originate in regions with higher precipitation and flow into arid desert environments. They bring water from outside the desert, often from mountainous or high-rainfall areas, providing vital water resources

94
Q

What are ephemeral streams in the desert?

A

This term reflects the transient and intermittent nature of these streams, which only flow during and immediately after rainfall events, but may remain dry for much of the year.

95
Q

What are playas in the desert?

A

Playas are flat, dry lakebeds found in desert regions, characterized by their smooth surfaces and occasional salt flats. They form in arid environments where rainfall is infrequent and surface water quickly evaporates, leaving behind fine sediment or evaporite minerals.

96
Q

What are saline lakes in the desert?

A

Saline lakes in the desert are permanent bodies of water that contain high concentrations of dissolved salts, often forming due to the evaporation of ancient inland seas or the concentration of salts in closed drainage basins.

97
Q

What are the two types of aeolian erosion?

A
  1. Deflation (blowout of loose material)
  2. Abrasion (pitting by flying sand grains)
98
Q

What are methods of Aeolian transportation?

A

Physical Geography Exam I (4 decks)

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