SCIENCE TEST 12/19

What is talus?

Talus is a pile of angular rocks and sediment that were deposited during a rockfall.

What happens when small broken rocks fall into fast-moving river?

The river picks up the rocks and moves them downstream.

Could a rock from a landslide continue to move after the initial mass wasting is over?

The rock could keep moving as long as gravity is the strongest force acting on it. The rock will likely come to rest on a flat, stable surface.

What could you conclude about the amount of sediment in a river if it is a slow-moving river and has no sandbars?

You could conclude that the river was carrying little sediment.

What kind of process would deposit a sandbar in a river: a constructive process or a destructive process?

A constructive process would deposit a sandbar in a river. Constructive processes build up features on Earth's surface.

Is a rock more stable on a hillside or a plain?

A rock is more steady on a plain. On a hillside, the rock can be pulled down by gravity if it is disturbed.

How can gravity be an agent of erosion?

Gravity can cause a rock to fall down a hill, moving it from the top of the hill to the bottom.

What are some ways that gravity shapes Earth's surface?

Gravity can pull large masses from a slope, leaving deposited material below. Gravity can cause the outer edge of a slope to break off and remain suspended. Gravity also can cause a slope to slowly creep downward.

What is something that can cause the layers of colors in rock?

Sediment could have been deposited in layers, which then hardened into rock. Then the rocks could be worn away by wind and water.

Why is sediment in a sand dune usually well-sorted? Explain

Sediment in a sand dune is moved over a long distance by wind, which tends to sort well.

What features suggest whether erosion or deposition created a landform?

Tall and jagged landform are often created by erosion. Flat, low-lying landforms are often created by deposition.

A mudflow occurs when water-soaked soil gets heavy. Why would the mass of the soil be a factor in mass wasting?

The force of gravity depends on the mass of the objects being attracted as well as their distance apart. When the mass increases, the pull of gravity increases and can trigger a mudflow.

What kinds of factors causes land to collapse?

The main agent for mass-wasting events is gravity. These events may be triggered by heavy rains or earthquakes.

Describe what occurs when ocean waves moves rocks back and forth on a rocky beach?

The waves cause the rocks to rub against each other, smoothing the rocks and making them smaller.

How easy would it be to cross a young stream, mature stream and old stream?

The young stream is narrow, but it might be hard to cross because it is on a steep slope, and the water is moving quickly. The old stream is slow, but it might be wide, making it harder to cross. The mature stream might be the easiest to cross, because it is not too wide and not too fast. Mature streams are the middle of the development stages.

Where would you find the most erosion in a river? Where would you find the most deposition in a river?

Water flow is fastest on the outside of each curve and slowest on the inside. There is more erosion in fast water, and more deposition in slower water.

Why would the addition of houses to a hillside increase the pull of gravity on the hillside?

Adding houses increases mass on the hillside. The pull of gravity increases as mass increases.

Why wouldn't an alluvial fan form at the point where a stream on a gently sloping hill moves onto a flat plain?

An alluvial fan forms when a stream slows down sharply at the base of a steep hill or mountain. This allows sediment to be deposited immediately in a small area. Alluvia fans are triangular in shape and is found where the mountain stream meets the plains.

In which part of an old stream is the water flowing slowest?

It flows slowest on the inside of bends.

What would happen if a waterfall increased in size and speed for many years?

It would likely erode more material and make any existing valley wider and deeper.

Why do some rocks break down faster than others?

Some rocks are softer than others, so they weather more quickly.

What can help prevent a landslide?

Vegetation can keep soil in place and prevent mass wasting.

How could ice cause weathering?

Water can break rocks apart as it freezes and expands within cracks in rocks.

How does water erosion form a cave?

Acid in the groundwater dissolves limestone and washes it away, forming a cave.

Creep moves too slowly to be noticeable. Why is it a type if mass wasting?

In creep, a large mass of rocks or soil moves downhill due to the pull of gravity.

How does ocean water erode coastlines?

Ocean water wears away soft rock, forming new landforms such as sea caves, sea stacks, and sea arches.

How could constructive and destructive processes work together to form a rounded mountain?

One possible answer is: A volcano could deposit lava and form a steep, tall mountain. Wind and water could gradually wear away some of the rock on the mountain and make it rounded.

You find a rounded rock next to a jagged rock at the mouth of a river. Both rocks are the same size. What could be true about these rocks?

One possible answer is: The rounded rock could have traveled father (traveling longer distances gives a rock a chance to change more and round out in shape more), or could be softer than the jagged rock (softer rocks break down more quickly and edges can round out).

How does a sandbar form?

Sandbars can form when sand drops out as the speed of a river slows down.

Why is sediment from a volcanic eruption often poorly sorted?

Sediment produced from a volcanic eruption is usually deposited quickly, as different-sized grains fall from the air. This sediment often does not travel after it is deposited, so it would not be well-sorted.

How can erosion sort sediment?

Sediment that is eroded over a short distance is poorly sorted, with grains of different sizes. As sediment erodes over a longer distance, it becomes moderately sorted (with grains of a small range of sizes) and then well-sorted (with grains of all about the same size).

Why do some types of rock erode more quickly than others?

Some rocks are softer than others. The softer rocks weather or erode more quickly than harder rocks.

What are some factors that affect the rate of erosion?

Weather, climate, the shape of land (topography), and the type of rock affect the rate of erosion.

How is a glacier different from an iceberg?

A glacier forms on land and moves slowly across it. An iceberg is a huge chunk of ice that floats in water.

How does a meander change the plain that a river is on?

A meander moves across a plain as the river erodes one side of a bank and deposits material on the other. This changes the plain.

Which would move farther in a stream over one year: a small rock or a medium-sized boulder?

A small rock would move farther than a medium-sized boulder because water can pick up and carry small rocks more easily than larger rocks.

How does an alluvial fan develop?

An alluvial fan often forms where a stream flows from a steep, narrow canyon onto a flat plain at the foot of a mountain.

How is an ice sheet different from an alpine glacier?

An ice sheet covers large areas of land and moves outward from a central location. An alpine glacier forms in the mountains and flows slowly downhill.

How can erosion affect the shape of sediment?

As rock fragments are eroded, they bump against each other, which can change the shape from poorly rounded to well-rounded.

Why is water able to move particles from one place to another?

As streams move downhill due to the force of gravity, they pick up sediment and move it downhill. Wave energy (from the wind) can pick up and move sand and rocks on beaches.

What causes a river to flow from side to side (with curves)?

As streams move to flatter land, they slow down and begin depositing material that eventually become curves.

How do you think erosion and deposition can affect rocks?

Deposition can form the layers in the rock, and erosion could form smooth surfaces.

What is a depositional environment? Where can sediment be deposited?

Depositional environments are locations where sediment is deposited. Depositional environments include swamps, deltas, beaches, and the ocean floor.

What are two examples of destructive processes that can change landforms?

Earthquakes and hurricanes are two processes that break down features on Earth's surface on Earth's surface and change landforms.

Which is a destructive force: erosion or deposition? Explain.

Erosion is a destructive force because it removes sediment from landforms.

True or False? A glacier leaves behind very smooth land as it moves through an area.

False - A glacier carves the land as it moves, leaving distinctive erosional features or piles of sediment and rocks

True or False? Landslides are a natural process that cannot be influenced by human activities.

False - Human development on steep slopes and removal of vegetation can contribute to landslides.

True or False? Different sizes of sediment tend to mix when being moved along by water.

False - Sediment tends to become sorted when being moved along by water.

True or False? A beach is a landform that does not change over time.

False - Wind blows sand and waves move sand and rocks on a beach, changing it over time.

How could the force of gravity change the way mountains and valleys look?

Gravity can cause rocks and mud to fall, eroding a mountainside and depositing material in a valley. Other factors - like rainfall, earthquakes, and lack of vegetation - can also contribute to both erosion and deposition below these landforms.

Why do materials on a slope often move downhill?

Gravity is a force that pulls matter toward the center of the Earth. When material is on a slope, it can be pulled down the slope by gravity.

Describe two characteristics of a mass-wasting event.

In a mass-wasting event, material moves in bulk, and gravity is the dominant cause of that movement.

What do landforms that are created by erosion often look like?

Landforms created by erosion are often tall, jagged structures with cuts in layers of rock.

What are some ways human activities affect water erosion?

Negative effects: People can build dams that prevent sediment form replenishing beaches. People can remove vegetation, allowing soil and sediment to water into water bodies. Positive effects: People can build structures, such as groins or retaining walls, which can help prevent the erosion of sand on a beach. People can build levees to prevent flooding and the accompanying water erosion.

Could there be deposition without erosion?

No. In order for sediment to be deposited, you need weathering to break down rocks into sediment and erosion to carry that sediment to a place where it can be deposited.

Why might layered beds form when sediment is deposited?

One possible answer: Layered beds might form if one type of sediment is deposited in a low-energy environment and then overlain with a different sediment. These two (or more) different types of sediment are deposited over time and form layers. For example, layers of sand and clay could eventually form layers of sandstone and shale.

Why do you think a rock could have smooth curves instead of sharp edges?

Over time, particles carried by water and wind could have smoothed the surface of the rock layers.

What are some ways human activities can increase or decrease the risk of mass wasting?

People can reduce the risk of a mass-wasting event by maintaining vegetation on steep slopes and not building on steep slopes.

Why are wind and water agents of both erosion and deposition?

Possible answer: Fast-moving wind and water can pick up and erode material. When the wind dies down or when water slows down, the eroded material is deposited.

Why might water be the agent that changed rock formations in a desert?

Possible answer: Many features in deserts were under water at some point and were worn away as the water retreated. These features would have been changed the most by water before the area became a desert.

Why don't all streams have (big) curves?

Streams that move down steep slopes are faster and don't deposit much sediment, so they don't form curves.

What are some characteristics of landforms?

Structure, elevation, and rock exposure are all characteristics of landforms.

Describe the stream development stages.

The young stream moves quickly as it flows down a steep slope. The mature stream slows down and gets wider as it flows down a gentler slope. The old stream moves slowly and forms meanders on a flat plain.

True or False? Windblown sediment can cut and polish exposed rock surfaces.

True - As sediment blows across rock, it can cut and polish rock surfaces.

How does water deposition change Earth's surface?

Water deposition builds new features on Earth's surface.

How does water erosion change Earth's surface?

Water erosion moves sand and sediment away from landforms. This changes their shape.

How could wind and water combine to form sea caves on a rocky shoreline?

Waves are produced by wind blowing water. The waves continually weather the shoreline and would erode the weathered rock, forming caves.

How are erosion and deposition related?

When agents of erosion slow down, some sediment can fall out of wind or water and can be deposited.

Why wouldn't you want to build a house in a floodplain?

When it rains heavily, the river associated with the floodplain moves into the floodplain and can destroy the house or other property or belongings.

What happens when strong winds blow in a sandy dessert?

When strong winds blow across sand, particles of sand can be picked up and moved to a different area.

How could the processes of erosion and deposition lead to the formation of an oxbow lake?

When two curves get close enough, the river can cut through to shorten its course. Sediment becomes deposited and cuts off the original curve. The cut-off curve becomes an oxbow lake.

How do wind erosion and deposition change the Earth's surface?

Wind erosion can carry away rock particles. Wind can also deposit windblown sand in a dune, or crumbly silt and clay in a deposit of loess.

If a mountain were made only of one type of rock, could it be eroded? How?

Yes, even though differences in the hardness of rock would not be a factor, there are other ways that rocks erode. A glacier could cut through the mountain, creating a U-shaped valley. Ice and plant roots could push into cracks and weather part of the rock, which could then be carried away by wind or water.

Is a landslide that occurs during an earthquake an example of mass wasting? Why or why not?

Yes. The earthquake shakes the soil loose, which makes it easier for a mass of soil to be pulled down by gravity.

Is it possible for a stream to be young, mature and old at the same time?

Yes. The headwaters of a stream may start in the mountains and be young. As it moves onto a gentle slope, it would slow down and become mature. As it moves onto flat land, it would slow down more and become old. (depends on slope of the land)

What kind of sediment would you expect to find on a rocky beach and why?

You can expect to find poorly sorted, poorly rounded sediment on a rocky beach because the rocks on the beachy will break down but have not have been eroded very far. Sediment on a sandy beach would likely be well-rounded and well-sorted, having been eroded by waves.

On an ocean shoreline you see a sandy beach just a few blocks down from a rocky beach. What might you infer about the forces at each location?

You might infer that waves are stronger at the rocky beach and that the rocky beach is not near the mouth of a river that would deposit sand and sediments. You might infer that the sandy beach could be near a river that deposits sand. You might also infer that the ocean waves at the sandy beach are slower and calmer, and deposit materials rather than wasting them away.

Would you expect to see little sediment or much sediment at the endpoint of a wide, slow-moving river?

You would expect to see much sediment at the mouth of a wide, slow-moving river. Most rivers deposit sediment when they reach their endpoint. The sediment can be deposited under water, or it can be visible above the water (a delta).