26. Erosion and Mass Wasting (P. 402-418)

Physical Geology 101

26. Erosion and Mass Wasting (p. 402-418)

Erosion

Where are two U.S. examples of where shoreline wave erosion is a major concern?

1. ______2. ______

Where is shoreline erosion also a problem at a large lake? ______

Weathering involves the breakdown of rock to form loose particles called regolith. Any process that involves the movement of this regolith from one location to another, and the abrasion of rocks hit by the regolith as it gets transported, is termed erosion.

What 3 natural “elements” cause erosion?

1. ______2. ______3. ______

What are the two characteristics of a flowing medium that play an important role in how effectively material gets transported?

1. ______and 2. ______

The resultant types of fluid motion are called ______and ______.

Describe laminar flow: ______

Is the flow speed high or low? ______

Describe turbulent flow: ______

Is the flow speed high or low? ______

Is turbulent flow more common in fluids with low or high viscosity? ______

So which is more turbulent: water flow or wind gusts? ______

When pieces of regolith get lifted up off the ground and then bounce it along in small hops and jumps, we call this process ______.

Mass Wasting

What fourth effect may cause a type of erosion called mass wasting? ______

What happens during mass wasting? ______

The common term used to describe mass wasting is ______.

1 Physical Geology 101

What main factors influence the motion of regolith down a slope?

1. ______2. ______3. ______4. ______5. ______

The susceptibility of loose material to move down a slope is affected by the way the grains of the material are packed together as well as the stickiness of the grains, which is called either the: ______or the ______

This stickiness of the grains determines a type of material strength called the:

______

What is the definition of this type of strength? ______

The steepest angle that a slope can maintain without material tumbling down is called the: ______

What is the range for this angle in most types of regolith? ______

The steepness of piles of ______that collect at the bottom of a steep slope is controlled by the angle of repose of the material.

Upsetting the angle of repose:

What activity by humans can induce landslide activity? ______

Removal of vegetation may induce landslides because roots bind regolith particles together, keeping them stable. Vegetation can be removed by humans or naturally by ______.

How does the addition of water destabilize sediment on a hill? ______This is why landslides are common after ______.

What other natural phenomena can induce landslide activity?

______(causes collapse of river embankments)

______(e.g. Yungay, Peru, 1970: 25,000 deaths)

Types of Mass Wasting

The three criteria used for classifying the different types of landslides are:

1. ______(rapid or slow) 2. ______(falling, sliding, or flowing) 3. ______(rock, soil, or debris)

We can define two categories of mass wasting / landslides:

 ______: falling, sliding, or slumping of otherwise coherent bodies of rock due to sudden failure on a steep slope or cliff.

 ______: fluid-like downslope movement of loose regolith.

What are the different types of mass wasting in each category?

SLIDES AND FALLS SEDIMENT FLOWS

______

Slides and Falls

What is a fall? ______

Example of where this is a problem: ______

What is a slide? ______

What is a slump? ______

Example of where slumping is common: ______

Sediment Flows

A sediment flow that is water-saturated is called a ______.

A sediment flow that is air-saturated is called a ______.

Water-saturated flows can occur very slowly in areas that typically receive lots of rainfall, and may form bulging lobes of migrating regolith on slopes. This process is called ______.

What is the difference in the sediment size between a mudflow and a debris flow?

Mudflow: ______

Debris flow: ______

How fast can a mudflow flow? ______

Examples of locations rapidly overwhelmed by mudflows:

(1) ______in 1985 (lahar induced by a volcanic eruption) (2) ______in 2006 (caused by heavy rainfall)

When a thin layer of water-saturated surface material (e.g. soil) flows down a slope over a period of days, months, or years, stabilized by a covering of grass, the flow is called an:

______

A dangerous variety of granular flow in which blocks of regolith race down a slope at speeds of 100s of mph, is called a ______. e.g., Peru, 1970 (triggered by an earthquake) - 25,000 deaths in the city of Yungay.

A slow type of granular flow can cause the imperceptible down-slope motion of an entire hillside. Objects on the surface eventually lean over. e.g. telephone poles, lampposts, fences, trees.

FINAL QUESTION:

What is this slow slope motion called? ______