Geology Chapter 16

Water erodes the outside of a river bend to form a __________.

cut bank

Which of the following would increase flow velocity?

having a narrow, deep channel

Which of the following choices does not directly affect stream velocity?

location of the drainage divide

What type of drainage pattern develops on highly jointed bedrock?

rectangular

Why are urban areas susceptible to flash floods?

A high percentage of the surface area is covered with cement, asphalt, and other impervious materials

The ________ describes the path water takes as it moves between the land, the ocean, and the atmosphere.

Hydrologic Cycle

How does the formation of a natural levee impact flooding?

Natural levees raise the height of the stream channel, reducing the amount of flooding that will occur on the floodplain.

Where are the headwaters of the Mississippi River?

Northern Minnesota

In the hydrologic cycle, water that falls on land in the form of precipitation returns to the ocean in which of the following pathways?

All of the responses are correct. (further precipitation, runoff, streams, groundwater flow)

What is the ultimate base level?

Sea level

Streams carry most of their sediment load in the form of suspended load.

True

How will the flow in this image affect erosion of the stream channel?

Turbulent flow contributes to erosion because it lifts particles from the streambed

What is infiltration?

Water soaking into the ground

What is a flood?

When discharge in a river exceeds the river's capacity

What is a stream's longitudinal profile?

a cross-sectional view of a stream from the headwaters to its mouth

What factors would decrease flow velocity? Select all that apply.

a decrease in stream discharge having a rough channel a decrease in gradient of the stream

Which of the following is the primary step that allows water to enter the groundwater system?

infiltration

How can pieces of rock in contact with a stream bed move?

rolling, sliding, bouncing

Which of the choices below is not a factor that causes infiltration and runoff to vary from place to place and from time to time?

time of the day

Complete this analogy: Bouncing is to sand as suspension is to_____________.

clay

Water in the hydrologic cycle readily moves from the land to the oceans through several pathways. How does the vast majority of water get from the ocean to the land surface?

clouds and precipitation

The process that causes dissolution of limestone bedrock in a stream is ______.

corrosion

What are water gaps?

erosion through hills or ridges caused by a change in base level

What type of stream is associated with the formation of an oxbow lake?

meandering stream

Which of the following rivers is the largest river in North America?

the Mississippi River

What is discharge a measurement of?

the amount of water flowing in a river

While working on a stream in your field study area, you find that the channel width is 20 meters, the channel depth is 2 meters, and the velocity is 1.2 meters/second. What is the discharge of this stream?

48 m3/s

What is the minimum velocity needed for a 0.8 mm sand particle transition from a state of deposition to transportation?

5 cm/sec

What is the geologic definition of a stream?

A channelized body of water flowing down gradient

Point bars are locations where erosion occurs whereas cutbanks are locations where deposition occurs.

False

What has caused the hypoxic "dead zone" to form off the coast of the Gulf states?

Fertilizers promote the growth of algae. When they die and decompose, oxygen is depleted in the Gulf of Mexico.

How does an alluvial fan form?

When a stream with a steep gradient emerges onto a relatively flat lowland, its gradient drops, and it deposits a large portion of its sediment load in a pattern that looks like a fan from above.

What is a floodplain?

a flat surface next to a river channel

What is a natural levee?

a ridge of flood deposits next to a river channel

Particles moving by saltation are transported in the _______ load.

bed

What are the three types of loads carried by streams?

bed load, suspended load, dissolved load

What is the dominant fluvial process in a clear, sediment-poor stream moving down a steep slope?

downcutting

Complete this analogy: Sliding is to gravel as dissolution is to_____________.

ions

According to the hydrologic cycle, once precipitation has fallen on land, what paths might the water directly take? Select all that apply.

runoff into a river runoff into the sea evaporation/transpiration infiltration into the ground

Which part of a stream's sediment load moves the slowest?

Bed load

What is the difference between capacity and competence?

Capacity is the maximum load of solid particles a stream can transport per unit of time, whereas competence is a measure of a stream's ability to transport particles based on size rather than quantity.

As stream velocity slows, the smallest particles get deposited first.

False

Rank the following sources of water from largest to smallest in terms of percentage of the world's total supply. Rank from largest to smallest. To rank items as equivalent, overlap them.

Largest: Oceans Glaciers Groundwater Non-glacial ice and snow Lakes Smallest: Rivers

At approximately what velocity will a 0.1 mm sediment particle begin moving in the stream?

0.6 cm/sec

________ is the maximum load of solid particles a stream can transport per unit time.

Capacity

How are oxbow lakes formed?

Oxbow lakes form when one meander erodes into another, cutting off water to part of the stream channel.

Transpiration moves water from _______.

the biosphere to the atmosphere

What is suspended load?

the fine-grained particles that travel in the water column above the stream bed

Each of these strategies has particular strengths and weaknesses. Fill in the following sentences with the correct type of flood control.

1. Besides flood control, a(n) dam can also be used to generate hydroelectric power. However, they are expensive to build and maintain. 2. Removing obstructions from a river channel is a form of a(n) channelization. It can make a river more navigable, but may also increase bank erosion due to increased water flow. 3. A(n) artificial levee confines water flow and can experience significant erosion. Constant maintenance is required. 4. Zoning regulation is/ are cheap to implement, but it/they can adversely affect property values.

Match the words in the left column to the appropriate blanks in the sentences on the right.

1. The geographical area where all surface water converges to one location is called its drainage basin. 2. A delta forms at the mouth of a river, where the velocity of the water flow decreases and deposition is highest. 3. The volume of water flowing past a certain point in a given amount of time is a river's discharge. 4. The headwaters of a river have a steep gradient, high channel roughness, and low water volume. 5. A stream with a low to moderate gradient, carrying most of its load in suspension, should be characterized by many curves and bends called meanders. 6. A river with a well-developed floodplain has a flat low-lying channel and experiences flooding during periods of high discharge.

A stream is transporting Particle A. The velocity of stream is decreasing, but for the moment, Particle A is still moving. However, when the water drops below 50 cm/sec, Particle A falls below its fall velocity and is deposited. Based on this information, what is the likely particle size for this object?

10 mm

What percentage of Earth's water is in the form of seawater?

97.2%

How did the Mississippi River delta form?

As the Mississippi River enters the Gulf of Mexico, its velocity decreases and it begins to drop its sediment load.

Where are bedrock channels more likely to be found?

Bedrock channels are typically found in the headwaters of river systems where streams have steep slopes.

X marks the site of oil drums that were illegally buried by the Shay-Dee Oil Corporation. These oil drums have begun leaking and the leaking oil has flowed downslope to the stream below, contaminating the stream. Which stream drainage basins would be affected by this oil?

C and A

________ is a measure of a stream's ability to transport particles based on size rather than quantity.

Competence

The ________ is an elevational point that divides an entire continent into large drainage basins.

Continental Divide

Which of the following statements about the global water supply is true?

Decreased precipitation could impact water supply available for humans.

Match the landform with the correct description. Drag the terms on the left to the appropriate blanks on the right.

Delta−form where streams enter large lakes or oceans. Levee−formed by floodwaters on either side of a stream. Alluvial Fan−formed by mountain streams emerging onto a flat plain. Bar−small deposits that form in the stream channel.

Where do deposition and erosion of material occur along a meander?

Deposition occurs on the inside of the meander, whereas erosion occurs on the outside.

Which of the following statements about deposition and erosion around meander loops is true? Choose all that apply.

Deposition occurs where water is moving the slowest along the inside of the loop. Erosion occurs where water is moving the fastest along the outside of the loop.

Match the type of sediment load to the correct definition. Drag the terms on the left to the appropriate blanks on the right.

Dissolved Load−ions in solution that are dispersed throughout the flow. Bed Load−larger sediments that bounce, roll, or slide along the bottom. Suspended Load−fine sediments that are held up by the water and carried throughout the water column.

________ are flat areas along streams that are created by the deposition of alluvium and is subject to periodic inundation.

Floodplains

During what periods would streams see the greatest erosion and transportation of sediment?

Floods

Which of the following particle sizes is most likely to make up a stream's suspended load?

Silt

Why doesn't sea level drop even though oceans have a higher rate of evaporation than precipitation?

Surface water running off into the oceans makes up the difference between evaporation from the oceans and precipitation into the oceans, creating a balance.

Using the information provided above, describe what changes will happen to the stream and its streamflow as the water moves from the head to the mouth.

The channel roughness and slope decrease while the discharge, channel size, and flow velocity increase

What will happen to the water level in the stream if the water table is below the level of the stream channel?

The stream will lose water to the groundwater system.

How will channel velocity change along the longitudinal profile of a stream?

Velocity will start low and gradually increase toward the mouth due to increasing discharge downstream

The amount of meandering that occurs in a stream influences the gradient in which of the following ways?

With more meanders, the stream gradient decreases.

What is an oxbow lake?

a meander that has been cut off from the original stream channel

What is a graded stream?

a stream that neither erodes material nor deposits it but merely transports it

A ________ stream consists of a complex network of converging and diverging channels that weave around channel bars.

braided stream

Describe the erosion occurring during headward erosion.

erosion backwards at the start of the stream

Which of the following locations contains the most water in Earth's hydrosphere aside from the oceans?

glaciers

Which of the following are part of the bed load? CHOOSE ALL THAT APPLY.

gravel sand

Velocity and turbulence are _____ at the __________.

greatest; outside of a meander

What is base level?

The downward limit of erosion.

What is the term for sediment deposited by streams?

Alluvium

Which of the following beds would be easiest for a stream to erode?

Lined with silt

Streams generally receive their water from two sources. What are those two sources?

Overland flow and groundwater

When considering the movement of water on Earth within the hydrologic cycle, which of the following choices is responsible for driving this process?

The hydrologic cycle works because water exists on Earth in solid, liquid, and gaseous states.

What is the mouth of a stream?

The location where one stream flows into another body of water

What are the three main zones of a river system from highest to lowest?

zone of sediment production, zone of transportation, and zone of deposition