Earth Systems Science: Mass Wasting, Streams, Groundwater

What four factors interact to cause mass wasting?

(1) Gravitational force, (2) normal force, (3) shear force, and (4) shear resistance.

What is mass wasting?

The movement of rock and sediment downhill due to gravity.

What role does water play in mass wasting?

A small amount of water helps hold sediment together, while too much water reduces friction and adds weight, enhancing mass wasting.

What is the angle of repose?

The maximum slope angle that a pile of sediment can maintain.

How is mass wasting classified?

Based on (1) type of material, (2) rate of movement, and (3) mechanism of failure.

What are the three types of failure mechanisms in mass wasting?

(a) Fall, (b) Slide, (c) Flow.

What is talus?

A pile of rock fragments that accumulate at the base of a slope/cliff due to rock falls and physical weathering.

What are the differences between rockslides and slumps?

Rockslides have a planar slip face, while slumps have a curved slip plane.

What defines flows in mass wasting?

The movement of unconsolidated material mainly defined by water content and rate of movement.

What are the four types of flows?

(a) Debris flow, (b) Mudflow, (c) Earth flow, (d) Creep.

What are lahars?

A type of mudflow that consists of volcanic ash.

What causes creep in mass wasting?

Freeze-thaw cycles.

What is the main function of streams in the hydrological cycle?

Streams are the main pathways by which water returns from the land to the ocean.

What is a drainage basin or watershed?

The land area that supplies water to a stream.

What forms at the mouth of a river in a desert environment?

An alluvial fan.

What forms at the mouth of a river underwater?

A stream delta.

How does stream gradient affect stream velocity?

The gradient is typically steep at higher elevations (faster velocity) and gentle at lower elevations (slower velocity).

What are braided streams?

Wide, relatively high-gradient channels with a large bedload.

What are meandering channels?

Streams with a smaller bedload and lower gradient that form large loops called meanders.

How does grain size change downstream in streams?

Average grain size decreases due to abrasion, and grain sorting increases as smaller grains are separated from larger ones.

What is stream competence?

The largest sediment size that can be transported by a stream, controlled by stream velocity.

What is stream capacity?

The amount of sediment a stream can transport, controlled by stream discharge.

What happens to streams over time due to erosion and deposition?

They often become sinuous, forming meanders and eventually creating oxbow lakes.

What is the water table?

The upper surface or level of the groundwater.

What is porosity?

The volume of pore space in sediment or rock that can hold water.

What is permeability?

The degree to which pore spaces are connected, allowing groundwater to move.

What are aquifers?

Sediment and rocks that can serve as a usable source of groundwater, characterized by high porosity and permeability.

What is an aquitard?

Rock or sediment that inhibits the movement of groundwater.

What occurs when water is pumped from an unconfined aquifer?

It lowers the water table and can create a cone of depression.

What is an artesian aquifer?

An aquifer confined above and below by aquitards, leading to built-up water pressure.