lol geo april/11 Flashcards
What is mass movement?
downslope of movement of rock, regolith, and soil bc of gravity, the most dramatic occur in rugged geologically young elevations
what triggers a mass movement?
Saturation with water- water fills pore space and reduces the cohesion & makes it heavier so it falls
steep slopes- cut toes & steeper angles increase gravities effect
removing vegetation- roots tie soil together
earthquake vibrations
What is a “fall”
Free fall of individual pieces of any size
What is a slide?
When a big chunk of material slides down in one piece, usually dry material
What is a slump?
When it falls off in layers, leaves noticeable scars, slow and common in clays
What is a creep?
Very gradual movement of surface soil, shows in the buildings or bent trees bc of the freeze n thaw/wetting and drying
What is a debris flow
Downslope flow after a lot of water saturates the soil
What is a lahar
Debris flow of the slope of a volcano, saturated with water
what is solifluction
soil flow, slow flow of water common to permafrost regions,
What is transpiration?
Release of water from plants
What determines how much water infiltrates versus how much absorbs
intensity & duration of rainfall
surface material
slope
type and amount of vegetation
What are rills
when sheet flow of water turns into tiny channels
Describe the areas of a river system from top to bottom
Headwaters/ sediment production- sediment starts at bedrock
zone of transportation- trunk streams move sediment
zone of deposition- either accumulate to make a delta or moved offshore
Describe the drain patterns
Dendritic- branching like trees, common
Radial- like wheel spokes, down a mountain
rectangular- on faulted bedrock
trellis- parallel patterns on alternating weak and resistant bedrock
What does cross-sectional shape of a stream mean
A slice across the channel. CS determines amount of flow in contact with the banks and bed, this is called the wetted perimeter
less w.p=less drag= faster flo
Ratios
Increases over distance: discharge, size, velocity
Decreases over distance: slope, roughness, amount of sediments
What is quarrying
removing blocks from the bed of a stream channel
How can sediment be transported?
Dissolved load- carries sediment, invisible, flows with the stream
Suspended load- greatest amt carried, visible, fine
Bed load- move through saltation, coarse materials
Capacity and competence
Capacity- max load of particles a stream can transport in a certain amt of time
Competence- measure of what size particle a stream can move
Bedrock channel vs alluvial channel
Bedrock-stream cutting into solid rock, like white water rafting
alluvial-a stream w a floodplain, change constantly
cut bank and point bar
A cut bank is on the outside and point bae is on the inside
Base level
Lowest elevation a stream can erode its channel. where the mouth enters
What makes a v-shaped valley
Fast moving water, rapids, waterfalls
What is a delta
accumulation of sediment where a stream enters the ocean
