The Middle Fork of the Salmon River flows for about $175$ kilometers ($110$ miles) through a rugged wilderness area in central Idaho. a. Is the river flowing in an alluvial channel or a bedrock channel? Explain . b. What process is dominant here: valley deepening or valley widening? c. I the area shown in this image more likely near the mouth or the head of the river ?

This satellite image show s portion s of the Ohio and Wabash Rivers in May $2011$. What is the base level for the Wabash River? What is base level for the Ohio River? (Hint : Referring to the figure will help.) Are either of the base levels you just noted considered ultimate base level ? Explain .

Heavy rains in late July $2010$ triggered the mass wasting that occurred in this mountain valley near Durango, Colorado. Heavy equipment is clearing away material that blocked railroad tracks and significantly narrowed the adjacent stream channel. a. What type of mass wasting likely occurred here? Explain your choice. b. Most of us are familiar with the phrase "One thing leads to another." It certainly applies to the Earth system. Suppose the material from the Durango mass-wasting event had completely filled the stream. What other natural hazard might have developed ?

The concept of external and internal processes was introduced at the beginning of the chapter. In the accompanying photo, external processes are clearly active. Describe the role that mass wasting is playing. Identify one feature that is a result of mass wasting .

The accompanying photo shows a footprint on the Moon left by an Apollo astronaut in material popularly called lunar soil. Does this material satisfy the definition we use for soil on Earth? Explain why or why not.

Describe how plants promote mechanical and chemical weathering but inhibit erosion .

Granite and basalt are exposed at Earth's surface in a hot, wet region . Will mechanical weathering or chemical weathering predominate ? Which rock will weather more rapidly ? Why ?

Because of the burning of fossil fuels such as coal and petroleum, the level of carbon dioxide $\left(\mathrm{CO}_2\right)$ in the atmosphere has been increasing for more than $150$ years. Should this increase tend to accelerate or slow down the rate of chemical weathering of Earth's surface rocks? Explain how you arrived at your conclusion .

This soil sample is from a farm in the Midwest. From which horizon was the sample most likely taken-A, $E, B$, or $C$ ? Explain.

Classify as mechanical or chemical weathering: cracks in a sidewalk next to a tree; limestone with holes like Swiss cheese; a rock that slowly turns reddish brown.

Refer to the accompanying photo to answer the following: a. The white line shows the approximate location of a fault that displaced these furrows created by a plow. What type of fault caused the offset shown? b. Is this a right-lateral or left-lateral fault? Explain .

The lowest notch shown on this figure is 9 meters wide and 5 meters high from its base. The river has a velocity of 1 meter per second when it fills the notch. Based on the accompanying graph, what is the probability each year that the notch will be filled to the top?

A. 90 to $95 \%$

B. 60 to $80 \%$

C. 40 to $45 \%$

D. less than $40 \%$

E. none of these

The three most common cementing agents in sedimentary rocks are?

Distinguish between porosity and permeability. Contrast aquifer and aquitard .