Mass Wasting and Erosion: Types, Triggers, and Prevention in Geology

What is mass wasting?

The movement of earth material down slope by gravity.

What is erosion?

The action of surface processes that removes soil, rock, or dissolved material from one location and transports it to another.

What are the main types of mass wasting?

Creep, slump, flows, slides, avalanches, and falls.

What factors control mass wasting?

Slope angle, material type, vegetation, water content, and earthquakes.

What is creep in the context of mass wasting?

A slow, gradual movement of soil or rock down a slope, often exaggerated by freeze-thaw cycles.

What distinguishes a slump from other types of mass wasting?

A slump involves a rotational movement of material that doesn't travel far from the original position.

What is a mudflow?

A slurry of water and fine sediment that moves rapidly down a slope.

What is a debris flow?

A mudflow that contains many large rocks.

What is a landslide?

A sudden movement of rock and debris that travels parallel to the slope.

What conditions can trigger mass wasting events?

Heavy rainfall, saturated soils, earthquakes, and human activities like deforestation.

What is solifluction?

The flow of water-saturated sediments over frozen ground, often resulting in lobes.

How does vegetation affect slope stability?

Roots anchor soil and help prevent erosion and mass movement.

What is the role of water in mass wasting?

Water can saturate sediments, reduce cohesion, and increase the likelihood of movement.

What is a talus?

A slope of loose rock that accumulates at the base of a cliff or steep slope.

What is the significance of the freeze-thaw cycle in mass wasting?

It can cause repeated expansion and contraction of soil, leading to increased movement over time.

What is the difference between a flow and a slide?

Flows involve a mixture of water and sediment, while slides are typically more cohesive and move as a unit.

What is the impact of human activities on erosion risk?

Activities like deforestation and construction can increase erosion risk by destabilizing slopes.

What are varves?

Layers of sediment that represent annual deposits, often found in glacial environments.

What is the primary force driving mass wasting?

Gravity, which creates a downslope force that can exceed resistance forces.

What are some remedies to prevent mass movement?

Drainage systems, vegetation planting, and retaining walls can help stabilize slopes.

What is a rotational slide?

A type of mass wasting where material moves down a slope in a rotational manner.

What is the relationship between slope stability and resistance force?

A slope is stable when the resistance force exceeds the downslope force.

What is the role of geology in slope stability?

Different geological materials can create glide planes that affect how easily material moves.

What can happen during a heavy rainstorm in relation to mass wasting?

Saturated soils can lead to increased erosion and trigger landslides or mudflows.

How does undercutting contribute to mass wasting?

Undercutting by rivers or waves can destabilize slopes and lead to landslides.

What is the significance of the Dawson, Yukon event?

It illustrates the impact of mass wasting on communities and infrastructure.

What is the impact of tropical storms on mass wasting in Massachusetts?

Heavy rains and saturated ground during storms can trigger significant mass wasting events.

clastic sedimentary rock

Sedimentary rock that forms when fragments of preexisting rocks are compacted or cemented together.

High energy in river/stream

erosion, high sediment load, large clasts move too

Low energy in river/stream

Low sediment load, only finest grained clasts move

Drainage Basin

the area from which a single stream or river and its tributaries drains all of the water - same as watershed

Watershed

An ecosystem where all water runoff drains into a single body of water - same as drainage basin

Drainage Divide

a highland or ridge that separates one watershed from another

drainage network

permanent vs ephemeral streams

permanent flows year round; receive a supply of water from upstream but also full with groundwater coming from streambed or channel - think about water table, temparate climate

ephemeral stream is only part of the year; dry during dry seasons - dry climate

dry wash

The channel of an ephemeral stream when empty of water.

Bed load

sediment that is carried by a stream along the bottom of its channel

Suspended load

The load contains small rocks and soil in suspension, which can make the river muddy

Dissolved load

The load contains dissolved materials such as sodium and calcium

Saltation

The movement of sand or other sediments by short jumps and bounces that is caused by wind or water

Dry day vs rainy day in stream

On a dry day, the stream flows slowly and the water is clear - clear water has dissolved load. On a rainy day, the stream flows fast and the water is muddy - suspended load and probably bed load

tributary

A stream or river that flows into a larger river

headwater

The source of a river

What is groundwater?

Water stored and moving very slowly underground in unconsolidated sediment or rock porosity.

What percentage of Earth's total water is found in oceans and seas?

96.5%

How much fresh water on Earth is found in ice and snow?

69.6%

What is the residence time of water in lakes and reservoirs?

Approximately 10 years.

What is the significance of the water table?

It indicates the depth of water below the surface and changes with precipitation.

What is the difference between unconfined and confined aquifers?

Unconfined aquifers have their upper boundary at the water table, while confined aquifers are bounded by aquitards.

What is Darcy's Law?

It states that the flux of water through a permeable formation is proportional to the hydraulic gradient.

What is hydraulic conductivity (K)?

A measure of the ability of water to flow through porous media.

What conditions lead to the fastest groundwater velocity?

High hydraulic gradient and high permeability.

What is the role of the hydrologic cycle?

It describes the continuous movement of water on, above, and below the surface of the Earth.

What is an aquifer?

Permeable sediment or rock that contains water, such as sandstone or highly fractured rock.

What is an aquitard?

Low permeability rock layers that slow or prohibit water flow, such as shale.

What is the potentiometric surface?

An imaginary plane where a confined aquifer's water would rise to if allowed to flow.

What is the importance of groundwater flow understanding?

It helps manage water resources and predict the movement of contaminants.

What are the main components of the water cycle?

Precipitation, runoff, evaporation, transpiration, and infiltration.

What is the average residence time of groundwater?

It can range from weeks to over a million years.

How does climate change affect groundwater in humid regions?

It may lead to increased precipitation and flooding, impacting groundwater recharge.

What is the significance of measuring water table elevation?

It helps in understanding groundwater availability and flow patterns.

What is porosity?

The percentage of rock volume that is open space, affecting water storage.

What is permeability?

A measure of how easily water flows through a material, determined by the connectedness of open pores.

What happens to the water table during dry periods?

The water table lowers due to reduced recharge.

What is the average flow rate of groundwater?

Typically ranges from 0.01 to 1.4 meters per day.

What are the primary uses of groundwater?

Irrigation for crops, drinking water, household use, and industrial use.

What is the relationship between topography and groundwater flow?

Water flows from higher elevations (high potential) to lower elevations (low potential), mimicking topography.

What is the impact of excessive groundwater extraction?

It can lead to land subsidence and depletion of water resources.

What are artesian wells?

Wells that tap into confined aquifers where water is under pressure, allowing it to rise without pumping.

What are the two main types of hydraulic gradients?

Low hydraulic gradient and high hydraulic gradient.

What does high porosity in groundwater indicate?

It indicates the ability of the ground to hold water.

What does high permeability in groundwater indicate?

It indicates the ability of water to flow through the ground.

Which water source does Amherst primarily use?

Surface water.

How does water consumption change throughout the year in Amherst?

It increases in Spring and Fall due to higher demand.

What is a 'Cone of Depression' in groundwater terms?

A cone-shaped decline in the water table around a well due to excessive pumping.

What is subsidence in relation to groundwater extraction?

The ground may collapse due to excessive water extraction, leading to permanent loss of aquifer space.

What is the significance of Joseph Poland's work?

He documented land subsidence in the San Joaquin Valley due to groundwater extraction.

What are the primary causes of flooding?

Heavy rain in a short time frame, snowmelt in Spring, and rain on snow.

What is the hypothetical situation regarding the UMass Farm?

Cows and goats escaping and damaging neighboring crops, leading to financial losses for farmers.

What decision does the Chancellor face regarding fencing at UMass?

Whether to repair the old fence or invest in new fencing, impacting tuition costs.

How does insurance relate to flood risk management?

Insurance protects against the financial burden of rare but costly events like floods.

What is the connection between medical debt and bankruptcy?

Medical bills accounted for 40% of bankruptcy filings, highlighting the financial impact of health issues.

What environmental issue is caused by groundwater dissolving limestone?

Formation of sinkholes.

What is saltwater incursion?

The intrusion of saltwater into freshwater aquifers, often affecting coastal areas.

What are point source and non-point source pollution?

Point source pollution comes from a single source (e.g., landfills), while non-point source pollution comes from multiple sources (e.g., agricultural runoff).

What is the impact of excessive fertilizer use?

Too much fertilizer can lead to groundwater contamination and environmental harm.

What are the two types of aquifers?

Unconfined and confined aquifers.

What is bioremediation?

A process that uses natural organisms to clean up contaminated environments.

What is phytoremediation?

Using plants to absorb and remove contaminants from the soil or water.

What is the purpose of reactive barriers in groundwater management?

To contain or treat contaminated groundwater as it flows through.

What does 'LUST' stand for?

Leaky Underground Storage Tanks.

What is the difference between LNAPL and DNAPL?

LNAPL (light non-aqueous phase liquid) floats on water, while DNAPL (dense non-aqueous phase liquid) sinks.

Igneous Rocks

Rocks formed through the cooling and solidification of magma or lava.

Magma

Partial melts of existing material in either the mantle or crust.

Melting Processes

Three processes cause melting: an increase in temperature, a decrease in pressure, or an addition of volatiles.

Intrusive Rocks

Rocks that cool below the surface.

Extrusive Rocks

Rocks that cool at the surface.

Partial Melt

A mixture of liquid (molten) and solid (crystal) components in magma.

Crystalline Mush

The mixture of liquid and solid components in magma, similar to a frozen margarita.

Crystals

Minerals in igneous rocks that do not have the nice shape associated with crystals but refer to the mineral components of the rock.