7c review questions
1. what process affects all rocks after they have formed? what kind of earth materials does this process create?
2. how are sediments moved about?
3. assume that sediments collect on the deep ocean floor at a rate of 3 cm per 1000 years. how old might the ocean floor be if sediments are 90 cm thick? is this a reasonable answer?
4. describe and compare mesas and buttes.
5. how are monadnocks different from most other erosional mountains?
6. what kind of depositional mountains or hills is formed by wind?
7. what is glacial till? give two ways that glaciers can move till.
8. why are volcanoes considered depositional mountains?
9. (true or false) some fossilized sand dunes seen in sandstone formations may have actually formed underwater.

Question

Accepted Answer

### For Question 3:
# Explanation:
## Step1: Identify the rate and total thickness
The rate of sediment collection is $3$ cm per $1000$ years, and the total thickness of sediments is $90$ cm.
## Step2: Set up the proportion
Let $t$ be the time (in years). We can set up the proportion $\frac{3\ 	ext{cm}}{1000\ 	ext{years}}=\frac{90\ 	ext{cm}}{t}$.
## Step3: Solve for $t$
Cross - multiply: $3t = 90	imes1000$. Then $t=\frac{90	imes1000}{3}= 30000$ years.
## Step4: Evaluate reasonableness
The ocean floor is constantly being subducted in some areas (due to plate tectonics), so in areas where subduction is active, the ocean floor is much younger. However, in areas with little subduction, this could be a reasonable estimate of the minimum age (since sedimentation is a continuous process but other factors like subduction can remove sediment).
# Answer:
The ocean floor might be $30000$ years old. Whether it is reasonable depends on the tectonic setting (e.g., in non - subducting areas it can be reasonable, in subducting areas it is not as the ocean floor would be recycled).

### For Question 1:
# Brief Explanations:
The process that affects all rocks after they form is weathering (and erosion). Weathering breaks down rocks into smaller particles. The earth materials created are sediments (through physical and chemical weathering and subsequent erosion and transportation of the broken - down rock material).
# Answer:
The process is weathering (and erosion); the earth materials created are sediments.

### For Question 2:
# Brief Explanations:
Sediments are moved about by agents of erosion such as running water (rivers, streams), wind, glaciers, and gravity (mass wasting like landslides can move sediments). These agents transport the sediment from the site of weathering to other locations.
# Answer:
Sediments are moved by agents like water (rivers/streams), wind, glaciers, and gravity (mass wasting).

### For Question 4:
# Brief Explanations:
Mesas and buttes are both landforms created by erosion. A mesa is a large, flat - topped hill with steep sides, usually wider (in terms of the top area) and formed from horizontal rock layers. A butte is similar but is smaller in size (narrower top area) and also has steep sides, often formed from the same type of rock layers as mesas but with more extensive erosion that has reduced its size compared to a mesa.
# Answer:
Mesas are large, flat - topped, steep - sided landforms; buttes are smaller, flat - topped, steep - sided landforms. Both form from horizontal rock layers and erosion, with buttes being smaller than mesas.

### For Question 5:
# Brief Explanations:
Most erosional mountains are formed by tectonic forces (like folding and faulting) and then eroded. Monadnocks are erosional remnants. They are formed when surrounding material is eroded away, leaving a single, isolated hill or mountain. Most other erosional mountains have a more complex origin related to tectonic uplift before erosion, while monadnocks are mainly the result of differential erosion (eroding the surrounding area more than the monadnock itself).
# Answer:
Monadnocks are erosional remnants (formed by differential erosion of surrounding areas), while most other erosional mountains have a tectonic origin (uplift) before erosion.

### For Question 6:
# Brief Explanations:
Depositional mountains or hills formed by wind are sand dunes. Wind - blown sand accumulates in mounds or ridges (dunes) as the wind slows down and loses its ability to carry the sand particles. Over time, these dunes can grow in size and form larger sand - based landforms.
# Answer:
Sand dunes are depositional mountains/hills formed by wind.

### For Question 7:
# Brief Explanations:
Glacial till is unsorted, unstratified sediment (including rocks, sand, clay, etc.) that is deposited directly by a glacier. Glaciers can move till in two ways: 1. By carrying the till within the ice (englacial transport) as the glacier flows. 2. By pushing the till in front of the glacier (push moraines are formed this way) or depositing it as the glacier melts (terminal moraines, lateral moraines).
# Answer:
Glacial till is unsorted, unstratified sediment deposited by glaciers. Glaciers move till by carrying it within the ice (englacial) and by pushing/depositing it as they flow/melt.

### For Question 8:
# Brief Explanations:
Volcanoes are considered depositional mountains because they are built up by the deposition of volcanic materials (like lava, ash, cinders) that are erupted from the volcano. As successive eruptions occur, these materials accumulate, building up the height of the volcano, which is a form of deposition (adding material to build the mountain).
# Answer:
Volcanoes are depositional mountains as they are built by depositing volcanic materials (lava, ash, cinders) from eruptions.

### For Question 9:
# Brief Explanations:
Some fossilized sand dunes in sandstone formations could have formed underwater. For example, in shallow marine environments, currents can create sand - wave structures that are similar to sand dunes. Over time, these can be fossilized in sandstone. So the statement is True.
# Answer:
True

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QUESTION IMAGE

Question

Explanation:

For Question 3:

Step1: Identify the rate and total thickness

Step2: Set up the proportion

Step3: Solve for $t$

Step4: Evaluate reasonableness

Answer:

For Question 1: