Earth Science - Chapter 18

What are Loess?

-fine-grained sediments of quartz, feldspar, hornblende, mica, and clay deposited by the wind -Very fertile soil and are great for grain-growing regions -Found in Northern China, central Europe, Midwest states in America

Describe Longitudinal dunes:

-long, ridges of sand that are parallel to the direction the wind blows

Describe Transverse dunes:

-long, wavelike patterns. Right angles to wind direction

What are Sea Stacks

-when Sea Arches collapse, they leave a column of rock in the water

Name 4 types of dunes:

1) Barchan- 2) Parabolic- 3) Transverse 4) Longitudinal

Wind carries two things for erosion:

1) Sand; 2) Dust

3 effects of relative Sea-level changes

1) Submergent coastlines 2) Emergent coastlines 3) Barrier Islands

Ways that wind moves sand and dust:

1) surface creep 2) Saltation 3) dust particles are light and suspended in the air

Describe sand movement:

Sand moves down a straight coastlines until it changes direction at bays and headlands The longshorecurrent will slow and deposit sand

What are ventifacts?

Ventifacts-rocks that have been pitted, grooved, or polished by wind abrasion Large rock structures in deserts were more likely formed by water erosion instead of by wind erosion

Describe erosion and formation of sea cliffs

Waves erode the coast and cause rock to collapse and form steep sea cliffs

What is a longshore current deposit?

Waves move individual sand grains move in a zig-zagmotion. General movement of sand along the beach is in the direction in which waves strike the shore

What are emergent coastlines?

When land rises or sea level falls -If an emergent coastline is steep and is exposed rapidly, it will errodeto form sea cliffs, narrow inlets, bays and wave-cut terraces -If part of the continental shelf is exposed, it will form a gentle slope -Costal plain, bays, headlands, many long, wide beaches

What are submergent coastlines?

When sea level rises or land sinks Divides become headlands with bays and inlets peaks may for offshore islands. Beaches are short, narrow, and rocky U-shaped glacier valleys produce deep bays with steep walls called fiords

What is wind deposition?

Wind drops particles when it slows down and can't carry them anymore Overlying layers causes cementation which makes sedimentary rock

Where is the greatest effect of wind erosion?

Wind erosion mainly affects deserts and coastlines Dry, soil with little vegetation Moisture makes soil stick together and makes it heavy

What are Tombolos?

beach deposit that connects an offshore island to the mainland

Describe Barchan dunes:

crescent-shaped dunes, open side faces away from the wind

Describe Parabolic dunes:

crescent-shaped dunes, open side faces into wind, long ends held by vegetation

What are Headlands?

high, steep formation of rock that extends out from the shore into the water

What are Bays?

indention in the shoreline due to an area of less resistant rock

What are Sea Caves-

large hole cut into the bottom of a cliff

What is a spit?

long, narrow deposit of sand connected at one end to the shore

What is sand?

loose fragments of weathered rocks and minerals Quartz, mica, feldspar, and magnetite

What are dunes?

mounds of wind-deposited sand When wind slows because of a barrier and drops its sediments, eventually it will burry the barrier

What is saltation?

movement of sand or other sediments by short jumps and bounces caused by the wind Move in direction of wind, never higher than 1 m

What is a longshore current?

movement of water parallel to and near the shoreline

What is a lagoon?

narrow region of shallow water between a barrier island and a shoreline

What are the dangers to coastlines?

oil spills, garbage, pollution from industry, sewage Hurricanes may greatly damage coastlines

What is dust?

particles smaller than the smallest sand grain Microscopic fragments of rocks and minerals (soil, volcanic eruptions) Plants, animals, bacteria, pollution, manufacturing processes

What is Deflation?

process where wind removes the top layer of fine, dry soil or rock particles

Describe how dunes move with the wind:

-If wind in same direction, dunes move downwind -Dunes usually move until they reach a barrier

Describe 3 ways in which shoreline erosion occurs:

1. Waves that hit the shoreline mechanically weather break rock fragments into small pebbles and sand grains 2. Severe storms can reshape shorelines noticeably in a single day 3. Salt water and air cause chemical weathering in rocks along the shoreline

What are beaches?

A deposit of sediment along an ocean or lake shore Beaches will form when more sediment is deposited than is removed

What is a berm?

A raised section deposited at the back of the sloping surface of the beach (only touched by waves during high tides or strong storms) During the winter-sand eroded and deposited offshore in a sand bar (long underwater sand ridge) During the summer-sand bar deposited back on the beach (widens beach)

Describe absolute sea level changes compared to relative sea level changes:

Absolute sea level changes when the amount of water in the ocean changes Relative sea level changes when the land or features near the coast change

Why are coastlines important?

Coastlines used for: fishing, shipping, industrial and residential development, and recreation

What determines the composition of a beach?

Composition of the beach depends on the source rock Coral, shells, river/glacier deposit, pebbles, etc.

Describe how coastal areas affect sea level changes:

Costal areas are constantly changing The sea level rises and falls over the over time.

Is the ocean higher or lower now than compared to in the ice age?

During the ice age the ocean was 140 m lower than it is now. The water was in the continental glaciers (had 70 million km3now only 25 million km3)

How long can dust from volcanoes be in the atmosphere?

Dust from volcanic eruptions may be in the atmosphere for several years

What are barrier Islands?

Long, narrow ridges of sand that lie nearly parallel to shore May form when the sea level rises over a flat costal plain and isolates dunes from the old shoreline May form when sand splits are separated from the land by storms Barrier islands tend to migrate toward the shoreline Storms may erode them quickly. Some erode at a rate of 20 m per year

What determines the rate at which sea cliffs form?

The rate depends on wave energy and on rock composition -Limestone-erodes rapidly, -granite-erodes slowly

What is surface creep?

sand grains rolled by the wind along the ground

What are Terraces?

when a sea cliff is worn into a nearly level platform (wave-cut terrace)

What is a Wave-built terrace-

when eroded material is deposited offshore and creates an extension to the wave-cut terrace

What is an estuary (example of a submergent coastline)?

when river valley covered a bay that has salt water and fresh water mix

What are Sea Arches-

when waves cut completely through a headland

What is desert pavement?

wind removes small particles and leaves closely packed small rocks protects the underlying soil