Dynamic Earth Exam 4

What can beaches be made from?

What is the difference between and summer and winter beach?

a. summer beach is smaller and narrow than a winter beach

b. A summer beach is bigger and broader than a winter beach

c. There is no difference between a summer and winter beach

b

What accounts for the difference between a summer and winter beach?

a In summer, the waves are smaller and gentle; depositing more sand than eroding

b In summer, the waves are bigger and stronger; eroding more sand than deposition

c There is no difference in a summer and winter beach; the waves do not change with the seasons

a

What is the name for the downshore movement of water caused by waves breaking at an angle to the shore?

a Downdrift Transport

b Surfzone

c Longshore current

d Drift movement

c

How does sand move along the beachface?

a Back and forth

b Down the beach with the longshore current

c Both back and forth AND down the beach with the longshore current.

c

How can a dam on a river affect a beach?

a It can stop the water that contributes to the longshore current

b It can stop sediment and cause a beach to narrow or disappear

c it can make dredging more difficult

d None of the above

b

 current that runs parallel to the shore

Longshore current

 balance between material that is deposited on the shore and the materials eroded away

Sediment Budget

sediment transported parallel to the shore-how sediments move

Longshore drift/longshort transport

Gently sloping fringe of sediment along a shore

beach

Opening or indentation in the shoreline that leads to a bay or lagoon

Inlet

Semi-enclosed body of water

Lagoon

A stretch of beach material that stretches into the sea and is connected to land on one end 

spit

An indentation formed at the base of a cliff when it is undercut by the sea

Wave Cut Notch

A rock arch formed from the weathering of a headland

Sea Arch

A column of pinnacle of rock formed from the erosion of a sea arch

Sea Stack

ability to flow 

Permeability

amount of empty space in a material

porosity

ground water flows through…

pores

High porosity and permeability needs

• loose material

• bigger grain size

• less cementation

• cracks store good ground water

rock or sediment holding a significant amount of groundwater 

aquifers

Good Aquifer

• Gravel 

• Sand 

• Limestone

• Certain sandstone (depending on how much cementation it has) 

• Igneous rocks with cracks

materials that prevent water flows

Aquitard

Common aquitard

Clay

shale

Unconfined Aquifer

open to the atomphere

Confined aquifer

confined beneath an aquitard, under pressure, artesian wells 

What drives groundwater flow?

Pressure

Recharge area

where water enters and flows down 

Discharge area

where water flows back up to the surface and may seep back out

Spring

natural outlet from which groundwater flows or seeps onto earth’s surface

Overpumping

when usage exceeds recharge

Subsindence

sinking land:removal of groundwater leaves pores empty, sediments compact under their own weight and land sinks

Cone of depression

water pumped out of water table too fast and lowers water table leaving dry wells

Glacial incorporation

 lose rock that is surrounded by glacier and is carried away 

Glacial plucking

a glacier breaks off fragments of bedrock

Glacial abrasion

sand and silt in ice grind away 

• Rock flour 

Striation 

• Grooves or scratches carved into bedrock 

  • Aligned in direction of flow

Cirque 

Depression at head of glacier

Tarn

Lake within a cirque

Arete

Sharp ridges between cirques

Horn

Pointed mountain peak surrounded by at least 3 cirques

U-shaped valley is formed by

glaciers

V-shaped valleys are formed by

streams

Roche Moutonee

Made from Bedrock; one side is smooth other side is steep; shape indicated flow of ice-starts at smooth and goes to rough side

Moraine

pile of sediment either carried on or left behind by glacier 

Glaciers are found in…

mountains and polar regions

Alpine glaciers

Forms in mountainous areas; flows from high elevations to low

Continental glaciers

aka ice sheets; broad, large not confined by topography

Basal Sliding

glacier glides along on wet sediment slurry-avoids friction from rock

Glacier

Ice that flows

• only happens at depths greater than 60m

Glacial advance

Accumulation is greater than ablation(melting)

Glacial Retreat

Ablation(melting) is greater than accumulation

Equilibrium line

between zone of accumulation and zone of ablation

Tidewater glacier

glaciers whose toe lies in the sea

Ice calves off of a tidewater glacier to form

an iceberg

What happens to sea level during glaciers?

it drops

Glacial substance

 pressure down on land-continental glacier

Post-glacial rebound

surface of continent rising back up after ice melts 

Pluvial lakes

Lakes made from rain water 

The ocean becomes enriched with which isotope during an ice age?

O18

Pleistocene ice age started how many years ago?

2.6 million

Milankovitch cycles

changes in earth’s orbit around the sun control amount of solar energy distributed on Earth

Ice Core

Orbital shape

earth’s orbit changes from more circular to elliptical over 10,000 years

Low eccentricity

perfect circle orbit

High eccentricity

oval orbit shape

Precession

the wobble of earth’s axis