Earth Science Ch 12 Study Questions

The image shows a cross-section (profile) of a hilly terrain. What is the relief between the hilltop and the river valley?

250m ex: Relief is calculated by subtracting the elevation of the lower point from the elevation of the higher point. In this case, we subtract the elevation of the river valley (~50 m) from the elevation of the hilltop (~300 m).

Which of the following phenomena may cause a stable slope to become so unstable that it fails? A.increased vegetation B.excavation at the base of the slope C.saturation D.vibration E.decreased slope F.increased load

B, C, D, F

What mass-wasting process most likely explains the tilting of gravestones in a hillside cemetery?

Creep Ex: Creep is slow, downhill movement of the ground surface that can tilt existing structures such as fences and gravestones. A slump and a mudflow do not move slowly and cause existing structures to tilt in this way. Liquefaction is not a process of mass wasting

The tragedy in 1970 at Yungay, Peru, was caused by which type of mass-wasting event?

Debris Flow ex: More than 18,000 people died when a debris flow, triggered by an ice flow following an earthquake, struck the market town of Yungay, Peru, on a busy market day in 1970. Mass movement can be slow (creep and slumping) or fast (debris flows and lahars). The town has not been rebuilt and the area is now a grassy meadow.

Mudflows that are triggered by volcanic eruptions, such as the mass-wasting events associated with the eruption of Mt. Pinatubo, are called

Lahars ex: Lahars are mudflows composed of volcanic ash mixed with water from melted snow and ice or from heavy rains. Lahars have the consistency of wet cement and can travel very long distances.

A river eroded away the base of the mountain slope it flowed alongside, causing a 400-m-wide slump to move downhill. The slump transformed into a mudslide at the base of the hill, which filled the river valley and buried a small community on the opposite bank. Where did this mass-wasting event take place?

Oso, Washington (2014) ex: One of the largest observed mudslides triggered by river erosion was the Oso, Washington, slide in 2014, which buried the community of Steelhead Haven, killing 43 people. The other events were triggered by different processes in other geologic settings.

This illustration shows the conditions that existed just before heavy rains caused the 1925 Gros Ventre Slide in Wyoming. The Gros Ventre Slide occurred as a slump that dammed the Gros Ventre River and created the Lower Slide Lake. Which of the following was primarily responsible for this famous event?

Shale A was responsible for the failure because it was mechanically weak and dipped in a downslope direction.

Slides with a spoon-shaped (concave upward) underlying surface are called

Slumps explanation: Creep, debris flows, and avalanches are types of mass movement that do not slide along concave surfaces.

Which of the following are reasons why the Moon's surface has remained mostly unchanged for 3 billion years?

The Moon does not have plate tectonics. Biological decay cannot occur on the Moon. There is no water on the Moon to cause weathering.

Climate is one factor that affects landscape evolution because it

affects the thickness of vegetation. Ex: Climate determines the thickness of vegetation in a region. Vegetation can either weaken the substrate or hold it together. The composition of substrate depends on the geologic history of a region, not on climate. Climate can determine whether liquid water, ice, or wind is the primary agent of erosion or deposition, but the speed at which water flows down a slope or whether soil stays put is controlled by the relief of a region.

Which of the following would increase the risk of a landslide?

allowing water to infiltrate the slope

Mass movement

depends on the difference between the downslope force and the resistance force. ex:Mass movement depends on the difference between the downslope component of gravity (downslope force) and the resistance force that prevents sliding. There is abundant evidence of submarine mass movements, including submarine slumps, debris flows, and turbidity currents. Mass movement can happen under wet (mudflows, lahars, debris flows, avalanches) or dry conditions and occur when the slope is steeper than the angle of repose.

Slump toe

depositional feature Can break apart like small thrust faults

Which of the following scenarios would be least likely to produce a mass wasting event?

dry, unconsolidated, irregular gravel with a slope angle of 40°

This image shows artificial ponds in the San Francisco Bay that are used to produce salt. The orange color comes from algae and brine shrimp that thrive in the ponds during the early stages of the process; the white material is salt that is almost ready to be collected. Which of the following parts of the hydrologic cycle causes the salt to become concentrated in these ponds?

evaporation

In the hydrologic cycle, the flow of water from the ocean to the atmosphere is via

evaporation ex: Evaporation is the process by which water enters the atmosphere from both freshwater and saltwater reservoirs.

Slump Scarp

exposes the failure surface Can break apart like small normal faults

Where is the majority of the Earth's freshwater (liquid or solid) stored?

glaciers, ice caps, snow EX: Frozen freshwater comprises about 2% of the total water on Earth, but it accounts for about 69% of the freshwater. Groundwater comprises about half that volume, and rivers and lakes much less than that.

In the hydrologic cycle, the water flow between reservoirs is driven by

gravity and solar radiation. ex; In the hydrologic cycle, the movement of water is driven by gravity and the Sun's radiation. The gravitational pull of the Sun and Moon control tides on Earth. Mountain-building and mass-wasting processes do not drive the hydrologic cycle.

Which of the following is a surface feature that indicates a slump is beginning to develop?

hummocky ridges ex Hummocky ridges are signs that a slump is beginning to develop. Foundations of buildings would be falling instead of rising. Slumps are not related to animal life in the area and do not develop on flat land.

Solifluction

is a kind of creep found on slopes that are underlain by permafrost. ex: Solifluction occurs when the surface layer in a permafrost region, such as the Arctic or a high-elevation region, thaws in summer and cannot drain through the underlying permanently frozen (permafrost) layer. This causes the soggy surface layer to flow downslope.

The Vaiont Dam area was vulnerable to mass movement because

limestone beds there dipped parallel to the mountain slope and were interlayered with weak shale. Ex:The weak shale beds interlayered with limestone, which were also parallel to the mountain slope, made it likely for mass movement to occur. Rock layers extending horizontally into a mountain slope would not cause a landslide hazard. There was no recent logging noted in the region, and the underlying bedrock was not granite.

The largest reservoir of water on Earth, whether saltwater or freshwater, is

oceans and sea ex: The largest reservoir of water on Earth by far is the oceans and seas.

Which of the following is a tectonic process?

rifting ex:Rifting is a tectonic process. Mass wasting, erosion, and deposition are surface processes that can occur anywhere on Earth's surface.

This image shows the aftermath of mass movement in a steep-sided glacial valley in Switzerland. This impressive scar and talus pile likely records which of the following types of mass movement?

rockfall

What kind of mass-wasting event occurred when the construction of the Vajont Dam in the Italian Alps caused water to infiltrate the bedding planes on the slopes of nearby Monte Toc?

rockslide ex: The Vajont Dam disaster involved a mass movement of rock, called a rockslide.

This image shows mass movement on a vegetated hillside near the Dietrich River in Alaska. Which of the following terms best describes this type of mass movement?

solifluction

Which of the following is a suitable method of managing mass wasting?

targeted, controlled explosions ex: Controlled blasting can remove loose, unstable material in a way that will do minimal harm but can prevent a more destructive event. Making the slope steeper, increasing subsurface water, or removing vegetation would all increase the likelihood of slope failure rather than decrease it.

Which of the following regions has the highest relief?

the Himalayan mountain belt Part 1 High-relief regions, such as mountainous regions, have significant changes in elevation over their areas. The Himalayas are the highest continental mountains on Earth.

One reason the landscapes on the Moon do not change as fast as Earth's landscapes is because

the Moon does not have mass wasting. ex:The reason landscapes change much faster on Earth is that Earth has plates, an atmosphere, a hydrosphere, and a biosphere. The Moon's surface is affected today only by micrometeorites and space weathering caused by radiation. Mass wasting does not occur on the lunar surface even though gravity is weaker on the Moon.

In the diagram pictured, if the angle of the slope is increased (made steeper), then

the downslope force (Fd) gets larger. EX: If the angle of the slope increases, the pull on the block from gravity increases and thus the downslope force increases

Landslides are likely to happen when

the downslope force becomes greater than the resistance force. ex:Landslides are likely to happen when the downslope force is greater than the resistance force. The angle of repose of sandy slopes is 30°-37°; angles greater than that will cause slope failure. Sliding happens on weak surfaces that parallel the slope, not dip into it. Adding weight to the tops of slopes, not the bottoms, may trigger movement

This picture shows a coastline that is rising relative to sea level. Which process may be responsible for the terrace featuresshown here?

uplift Ex: The terraces represent an older shoreline positioned above the modern shoreline. For terraces to form, sea level must have dropped relative to the coast. This drop can happen through global sea-level drop, or by uplift of the coast. Subsidence (sinking) and erosion reduce the elevation of the Earth's surface.

This image shows a series of beach deposits along the coast of Nunavut in northern Canada. The modern beach is at the bottom of the hill adjacent to the ocean. Near the top of the hill, the deposits are several thousand years old. Which of the following is the most likely explanation for the dynamic behavior of the Earth's crust at this location?

uplift caused by glacial unloading

Which of the following is a typically weak surface that geologists recognize as a potential failure surface?

wet clay layer ex: Typical failure surfaces include metamorphic foliation planes, wet clay layers, and joints. Crystalline igneous rocks like granite and basalt, and glassy igneous rocks like obsidian are strong substrates that do not usually contain zones of weakness.