Geology 102 - Content After Midterm 2

Mass wasting, glaciers, surface water, and groundwater.

mass wasting

Movement of Earth materials down a slope due to gravitational force

Mass wasting is influenced by what 3 factors?

Material characteristics, Water content, and Slope steepness

Surface tension

The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules

Human activities that can cause mass wasting?

• Adding weight • Slope steepening • Increasing moisture • Removing vegetation

Creep

Gradual downslope movement of soil or regolith

Solifluction

Freeze-thaw activity generated mass movement • Thawed water saturated soil flows over frozen layer underneath

Curved

rotational slope failure, e.g. slump

Flat

translational slope failure, e.g. rock slide

Slumping

Concave and cliff-like scarp (steep slope)• Block moves coherently (as one unit) along the failure plane • Often form stair step pattern of displaced blocks

Rock Slide

part of the bedding plane of failure passes through compacted rock and material collapses

Rock Fall

fast-moving landslide that happens when rock or earth falls, bounces, or rolls from a cliff or down a very steep slope

Mud Flow

a rapid, thick, and viscous flow of water and sediment that moves down a slope

glacier

Large, long-lasting river of ice that forms on land, undergoes internal deformation, and creates glacial landforms

Where do glaciers form?

at high elevation, high latitudes

Temperate glaciers

Glaciers that are near their melting point • Have meltwater coming off them year round

Polar glaciers

ice in the glacier is frozen year round. • Ice loss primarily from sublimation.

Subpolar glaciers

Between polar and temperature climate conditions • Experiences seasonal melting and water runoff

Valley glaciers

found in valleys, extending out from mountains

Cirque glaciers

form in cirques

Piedmont glacier

form where valley glaciers spread out onto a flatter area in a larger valley or on a plain

Icecaps

small ice sheets, form at high elevation

outlet glaciers

extend outward from continental glaciers or icecaps

Ice shelf

where a glacier extends out over water

Glacial Till

Unstratified and unsorted sediment deposited by glaciers

Esker

sorted sediments deposited by a river flowing under or through a glacier

Kettle lakes

depressions left by melted ice blocks

Outwash plains

Found at the terminus end of glaciers • Water transports sediments deposited by the glacier

Roches moutonnées

Hill features formed at the base of glaciers • Glacial plucking on the downstream side creates jagged cliff • Upstream side often has striations, smoothed

Isostacy

The crust “floats” on the mantle, and the level it floats at depends on the weight of the crust.

Isostatic rebound

as mass is removed through an ice sheet melting or erosion, continents “float higher”

Oceanic circulation

Thermohaline circulation driven by temperature and salinity gradients• Has a big influence on global climate patterns

Younger Dryas

• ~1200-year cold period started about 13,000 years ago. • Recovery from the last glaciation was abruptly reversed and glaciers expanded significantly.

Hydrology

Study of the movement, distribution, and quality of water

The Hydrologic Cycle

• Liquid (water) • Solid (ice) • Gas (water vapour)

Drainage Systems

comprised of streams and rivers • runoff enters channels, which join other channels to form a drainage system • total area feeding water to a drainage system is a watershed

Drainage divide

topographic high that separate watersheds

Discharge

the volume of water flowing through a river at a specific point per unit time

Laminar Flow

fluid travels smoothly or in regular paths

Turbulent Flow

speed of the fluid at a point is continuously undergoing changes in both magnitude and direction

Thalweg

The part of a stream with the highest flow velocity

Straight Channels

Found in locations where stream is forced to be straight by the local geology

Meandering Channel

Common in locations where a river is free to roam across a valley floor (unconfined)

oxbow lakes

Produced when a meander is cut off from the main channel

Braided Channels

Found in locations where the stream contains more sediment than it can transport

Graded streams

Section of a stream that has dynamic equilibrium between sediment supply (deposition) and transport

Aquifer

unit of rock or unconsolidated sediment through which groundwater can flow

Vuggy texture

Caused by dissolution of rock• Forms holes in the rock “vugs” • Common in carbonate rocks

Permeability

The capacity of a porous material to allow fluid to flow through it

Groundwater Recharge

snowmelt and rainfall that infiltrate and reach the water table

Hydraulic head

the level groundwater rises to in a groundwater well

Aquifer Subsidence

Extraction can decrease water pressure in pore spaces of aquifers • Can allow aquifer to compress causing depressions