UNIT 8 - STUDY GUIDE
Weathering 8.1
There are 2 types of weathering; physical weathering and chemical weathering.
Agents of physical weathering are: temperature changes, pressure changes, plant and
animal action, water, wind and gravity.
- Nature causes physical weathering by ice wedging, exfoliation, animals digging
burrows, plant roots widening cracks in rock.
- People cause physical weathering by digging up land for construction of homes
and businesses.
Agents of chemical weathering are: reactions with oxygen, reactions with acid
precipitation, reactions with acids in groundwater, and reactions with acids in living
things.
- Nature causes chemical weathering by oxidation, dissolving rocks
underground, lichens and mosses, and by leaves decaying.
- People cause chemical weathering by burning fossil fuels that pollute the
air which leads to acid rain.
Erosion & Deposition by Water 8.2
Water moves millions of tons of rocks and sediments every day, and creates many types
of landforms. Examples of these landforms are: canyons, floodplains, alluvial fans,
deltas, beaches, sandbars, and barrier islands. Some of these landforms are created by
erosion, others are created by deposition.
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Erosion creates canyons over millions of years when flowing water cuts into
the land below it, and removes all of the rocks and sediments.
Deposition creates deltas when a stream empties into a larger body of water
and drops its sediment. An alluvial fan forms when a stream slows down and
ends. It then empties all of its sediment on land.
Erosion and deposition of a river is affected by: gradient (how steep the slope is), load
(size and amount of sediments in the water), and discharge (amount of water). If there
has been little rain and the water level of the river is low, there will be little movement of
the sediments. If there has been a lot of rain, the water level will be high, and there will
be more erosion.
Flooding from storms increases deposition on floodplains AND increases deposition into
deltas.
It takes 2 steps to make a beach. The first step is: rocks and shells must be broken down
by physical AND chemical processes into very small pieces. The second step is: those
pieces must be deposited on the shoreline.
Sand dunes can be found along coastlines (beaches) and in desert areas. Blowing sand
grains move faster than falling or bouncing sand.
Erosion & Deposition by Wind, Ice, and Gravity 8.3
Wind, ice, and gravity shape Earth’s surface by moving sediments and creating
landforms.
Wind – causes abrasion by sand-blasting, and creates desert pavement by deflation (the
removal of fine sediments, leaving the rocks behind). Depositing sand creates dunes
along shores and in deserts. Loess is the thick build up of very fine sediments (dust) over
thousands of years.
Ice – glaciers are large masses that form when multiple snowfalls don’t melt, but instead
get pressed into harder and harder ice. Gravity causes glaciers to move downhill, pick up
rocks and soil on the way, and grind the land below it. Glaciers erode V-shaped valleys
into U-shaped valleys.
Gravity – causes mass movement of rocks and soil. It can be rapid, or slow moving.
Examples of rapid mass movements of land are: landslides, rockfalls, and mudslides. An
example of a slow mass movement of land is creep (when the top layer of soil on a steep
slope moves slowly downhill, causing tree trunks to bend as they grow).
Landforms and Florida 8.4
Florida has many landforms that were created by erosion and deposition. Some of these
landforms are: sinkholes, lakes, rivers, a delta, sand dunes, and a dynamic (always
changing) coastline. Florida does not have any mountains, or glaciers.
Sinkholes are formed when an underground cave collapses from the weight of the land
above it. If the bottom of the sinkhole becomes plugged with sediment, then it can get
filled with rain water, and a sinkhole lake is formed.
Historical facts: sediments that eroded from the Appalachian Mountains traveled south
and created layers of sedimentary rocks in Florida, and contributed sand to our beaches.
Large glaciers caused sea levels to drop, making the land area around Florida to be larger.
When those glaciers melted, sea levels rose, and Florida became the shape it is today.