Transcript deposition - Tapp Middle School

a.k.a.
THE MOLDING OF THE
EARTH’S UPPER
LITHOSPHERE
Erosion
•A natural process by which the earth’s particles are
removed with the forces of water, wind, gravity
and/or glaciers
Deposition
•A natural process by which the earth’s particles which were removed from their origin by the forces
of water, wind, gravity and/or glaciers - accumulate
in a new place
The natural processes of erosion and deposition
form many geographical features of the
continental crust of the earth’s lithosphere
Wind
Erodes mainly through deflation (a fancy name for the
blowing of surface material). The stronger the wind the
heavier the material that can be moved. As the wind weakens
or when an immobile barrier occurs, the wind drops the
particles (deposits them)
Wind Erosion
The two major landforms created by
wind deposition are:
Sand dunes
Loess regions
Glaciers
There Are Two Types of Glaciers
• valley glaciers, long
narrow glaciers which
usually move down
valleys cut by rivers
• continental glaciers which
spread out in all directions
covering the land
Glacial Erosion
Glaciers erode in two ways: plucking and abrasion.
Plucking: When glaciers flow over the land they
pick up rocks beneath them often breaking the rocks
apart into fragments which then freeze to the glacier
(these rock fragments can be huge boulders)
Abrasion: As the glacier moves it drags the rocks
with it gouging and scratching the bedrock as it goes
Some landforms due to the glacial
erosion process
Horn: glacier
carves away the
sides of a
mountain,
leaving a
sharpened peak
Fiord: valley
carved by a
glacier in a
coastal region
that fills when
the level of sea
rises
Cirque: bowl-shaped
hollow eroded by a glacier
Lakes: long basins
created by plucking
and abrasion
Glacial Deposition
As the glacier melts it deposits the sediment and rock (called till) it
eroded from the land creating various landforms.
Drumlin:
deposits
shaped by
retreating
glacier
Moraine: glacier deposit
mounds or ridges of
particles from sand to
boulders along the edge
of the glacier
Kettle lake:
forms when a
depression left
by a retreating
glacier fills
with water
Gravitational Erosion
The downhill mass movement of rocks and other materials.
The four kinds of
gravitational
erosion are:
•
•
•
•
creep,
landslide,
slump,
mudslide.
creep
Slow slide of
soil. Note the
bending of the
trees’ trunks.
Landslides and Slumps are very similar in nature. Landslides are
when rock and soil move quickly down hill. Slumps are large masses
that move down in a single “lump” of soil and rock.
Slump
 Landslide
Mudslides
The rapid downhill
movement of a
mixture of water,
rock and soil.
The amount of
water in a
mudflow can be
as high as 60
percent. Clay
soils suddenly
become
extremely fluid.
Water Erosion
Water is the most
common source
of erosion on
the Earth.
Water Erosion
Water erosion occurs
with the movement of
water on Earth’s solid
surface (called surface
water) and below it
(called groundwater).
It occurs with both fresh
water and salt water.
When it rains-it erodes!
• Raindrop impact begins the process of
erosion. As drops hit unprotected soil
they dislodge some particles making it
easier to move the soil with the water
during runoff.
•Rain and the soil it carries
moves downhill, with the aid
of gravity, forming rills and
then gullies until it reaches a
“permanent” holding place
such as a stream, river, lake or
ocean.
Rills
Gully
Creeks, streams and rivers are just gullies that stay
filled with water year round. They constantly erode
the soil around them cutting into the ground and soft
rock below. One of the most famous formations
caused by river erosion is the Grand Canyon.
Waterfalls form when the river erodes the bed
beneath unevenly. Softer rock gets removed
first. Harder rock erodes more slowly.
Click here to see animated version of waterfall formation.
The amount of sediment a river
carries with it is called its load.
Load is affected by the river’s slope, volume
flow and streambed shape.
– The steeper the slope, the faster the river flows
and the more sediment the river carries
– The greater the volume of water the more
sediment the river carries
– The wider and shallower a river is the more soil
surface area is exposed to the moving water and
the more sediment the river carries
Water Deposition
As the river’s flow begins to slow, the river begins to drop
its sedimentary load. This is called deposition. Two
common landforms created by these depositions are below.
Delta
Alluvial fan
A floodplain is a flat area along a river that receives
river deposition when the flood waters recede.
1
Meanders and oxbow lakes
are formations created by a
river’s erosion and
deposition. They form on
flat plains with an overall
slow current.
2
3
4
Groundwater
Erosion
After a storm some rain
gets absorbed into the
ground and becomes
groundwater. When
groundwater combines
with carbon dioxide it
forms a weak acid called
carbonic acid. When this
acidic water comes into
contact with limestone it
chemically weathers the
stone away forming
pockets or caves.
stalactites – C for ceiling
Different formations
inside caves are a
result of deposition,
such as stalactites.
and stalagmites
stalagmites – G for ground
If the roof of the cavern collapses a sinkhole is formed. This
can happen when water in the cavern, which is supporting the
ceiling, is removed.
WAVE ACTION
• Waves are constantly
working on the shoreline,
mainly by mechanical
action (impact and
abrasion) also known as
mechanical weathering.
Beaches change through
longshore drift. This
movement of the beach
sediment with the current
and motion of the waves
is a natural process that
makes beaches ever
changing
Waves create sea caves by
erosion. If the cave deepens
enough to work its way to the
other side of the rock it opens up
to a sea arch. If the arches top
erodes it becomes a sea
stack.
WAVE DEPOSITION
Many landforms are created by
wave deposition such as spits,
tombolos and barrier islands
Images and Data
courtesy of:
Van Buren County Community Center
Clark County Soil and Water
Conservation District
NRCS
canyoneers.co.uk
David Miller, USGS.
GeoBytesGCSE
http://www.monsted-kalkgruber.dk
swfwmd.state.fl.us
www.winona.edu
Landsat 7 ETM+ image
faculty.weber.edu
Power point created by Donna Marcelo