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Flashcards in Quiz 3 Deck (87)
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1

How do all rivers function with respect to create diverse landscapes?

They erode, transport, and deposit sediment.

2

What is one of the most important factors in the ability of a river to move water and sediment?

The velocity of water.

If water is moving over rough bottom (gravel and boulders for example), there’s more resistance, slowing velocity down.

If water is moving over mud and clay, there’s less resistance, so velocity is faster.

3

How does the texture of a river bottom influence the stream velocity?

The roughness influences the velocity

4

What is the quantity of water moving in a river called?

Discharge

5

Does discharge increase, decrease, or remain constant downstream?

Increases

6

Three erosional processes that act in rivers. What is hydraulic action?

It’s the turbulence of a rapidly flowing stream applies vertical forces that can lift sedimentary grains off the bottom.

Flowing current pushes against these particles and carries them downstream.

7

What is the process of scour through sediment or rock called?

Abrasian

8

What controls the erosion process called dissolution?

Mineral composition of the bedrock temperature, acidity of the water, and flow velocity.

9

Meandering rivers are associated with which geological hazard?

Flooding

10

How frequently do floods tend to occur, on average?

Every 2.5 years

11

Why are floodplains good places to grow crops?

Because when flood occurs, the water carries a muddy sediment, rich in organic matter and nutrients

Sediment is deposited in flat layers atop the floodplain and is naturally irrigated by flood waters

12

What is the hazard of living on a floodplain?

Damages to homes and cities, some sometimes people who live there.

13

What problems are associated with building levees?

They may confine sediment (raising the riverbed higher and higher)

Provide false sense of security

14

Does erosion increase or decrease directly downstream of a dam?

Increase (sometimes severely)

15

The basis of river dynamics is a balance of what three processes?

Erosion

Transportation

Deposition

16

In what situation is sediment deposited at Red Eye Crossing?

Here, river tends to deposit sediment, threatening to close channel to deep-water ships, not enough energy in water to clear that crossing out.

They use dredging to keep open, to make sure it’s deep enough.

17

How do dikes have the potential to reduce sedimentation in a stream?

They help to eliminate point bars.

They open the channel and make it wide and deep.

18

On average, how many people die per year in floods in the United States?

About 100 people every year.

19

What does the rock cycle explain?

-It explains interrelations among earth minerals

-consists of rock pathways

-attributed to James Hutton (1726-1797), the founder of modern geology

-rocks are continually changing from one type to another and back, as forces inside earth bring them closer to the surface (where they are weathered, eroded, and compacted) and forces on the earth sink them back down (where they are heated, pressured, and melted)

-elements that make up rocks are never created or destroyed, they’re recycled

20

What are the three main types of rocks?

Igneous

Sedimentary

Metamorphic

21

Describe Igneous Rock.

Formed through cooling lava and solidification of magma or lava

Can be changed into sedimentary or metamorphic rock

Two types -
extrusive (on earth’s surface)(volcanic)
intrusive (cools in magma chamber)(plutonic)

many related to volcanoes

look in packet 3/1/17!

22

Describe Sedimentary Rock.

Form by deposition of material at Earth’s surface and within bodies of water (like rivers)

Made up of sediment, which is bits and pieces of other rocks and/or organic materials (e.g. fossils)

Can change into metamorphic or igneous rock; form on surface (less than 100%)

Two types - clastic, sedimentary

*Sedimentation is the collective name for processes that cause mineral and/or organic particles (detritus) to settle and accumulate or minerals to precipitate from a solution

23

Describe Metamorphic Rock.

Form when rocks are subjected to heat and pressure from burial or contact with intrusive or extrusive igneous rocks (rock that was once one form of rock, but has changed to another under the influence of heat, pressure, or some other agent without passing through a liquid phase)

“Meta” means “change”, and “morph” means “form”

Heat and pressure from burial cause flat minerals (like mica) to align

Can change into igneous or sedimentary rock

Three types - contact, regional, shock

24

What are the six pathways?

Heat and pressure

Crystallization

Melting

Uplift

Weathering, erosion, and deposition

Compaction and cementation

25

What is metamorphism?

-Change occurs primarily due to heat, pressure, and the introduction of chemically active fluids.

-Occurs near magma chamber or by burial at great depth

-Alteration of the minerals and textures of a rock by changes in temperature and pressure, and/or by a gain or loss of chemical components

-Process that changes sedimentary and igneous into metamorphic

-These transformations take place in solid state. Grains get larger, different minerals may crow, crystals (grains) may change shape, grains or crystals may change orientation

-May change rock strength, so relevant to geohazards

-Occurs most noticeably along plate margins, especially convergent margins

-Large portion of continental crust is made of igneous and metamorphic rocks. Much of the thin surface covering of the crust is sedimentary rocks

26

Three types of metamorphism?

1)Contact Metamorphism: increased T, changes in Xfluid

2)Regional (dynamothermal): metamorphism: changes in P, T and Xfluid

3)Shock Metamorphism: ultrahigh P, high T (meteorite impact

27

What is erosion?

Processes that loosen sediment and move it from one place to another on Earth’s surface.

Agents: water, ice, wind, and gravity

28

What is weathering?

-Breaking down of rocks, soil, and minerals as well as artificial materials through contact with Earth’s atmosphere, biota, and waters.

-No chemical changes.

-Occurs in “situ” (with no movement). Don’t confuse with erosion, which DOES involve movement/transport

29

What are the two types of weathering?

1) Physical weathering involves breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water, ice, and pressure

Not chemical because no new material created

2) Chemical weathering is process by which rocks are decomposed, dissolved, or loosened by chemical processes to form residual materials

Chemical reactions break down bonds holding rocks together, causing them to fall apart into smaller and smaller pieces

30

What happens to sediment during transportation?

Carries sediments (or other materials) away from their origin

Transporting media include: wind, water, and mantle convection currents