Chapter 7 Student Presentation Notes
2nd Block


Types of Glaciers (Savannah & Cecilia)
o A glacier is a thick ice mass that forms over hundreds /
thousands of years
o Glaciers cover nearly 10% of Earth’s land area and contain a
lot of Earth’s freshwater
o Glaciers accumulate, transport, & deposit sediment = they
are an important part of the rock cycle
o Valley Glaciers
 Stream of ice that flows between valleys from a place
near the top of a mountain
 Can be short, long, narrow, wide, and have branching
tributaries
 Slow moving only advance a few CM to M a day
o Ice Sheets
 Enormous ice masses that flow in all directions and
cover regions where climate is extremely cold
 Larger than Valley Glaciers
 “Continental Ice Sheets”
 Antarctic ice sheet holds 80% of the world’s ice, and
2/3 of the Earth’s freshwater
How Glaciers Move (Ben & Sebastian)
o Plastic flow involves movement within the ice
o Normal brittle ice changes shape – plasticity
o The weight of overlaying ice exerts pressure on the ice below
causing it to flow
o Rates of Glacial Movement
 Plastic Flow
 Basal Flow
 Some glaciers are so slow that vegetation and trees
can grow on the debris
 Others can advance several m a day
o Basal Slip
 Uppermost zone of a glacier is brittle & is referred to
as the zone of fracture
 The Zone of Fracture experiences tension when it
flows over rough terrain

 Tension causes cracks called crevasses
o Budget of a Glacier
 Glaciers form where more snow falls than can be
melted in the summer
 Snow accumulates and ice forms at the head of the
glacier called the Zone of Accumulation
 Snowfall thickens and causes movement
 Area beyond the snowline is called the Area of
Wastage
o How Glaciers Move
 Calving creates icebergs when ice meets the ocean
 Calving is just massive chunks of ice breaking off the
edge of a glacier
 Icebergs are less dense than water which causes then
to float
 When you see an iceberg you only see the top 10% of it
so literally you are seeing the tip of the iceberg
Glacial Erosion (Carolina & Macy)
o Ice tears rock from the inside of valleys
o Hold everything they pick up until they melt
o From the most recent ice age landscapes were changed by
glaciers
o Plucking
 Surfaces of rock beneath glaciers are broken up as
melted glacial water penetrates the cracks
 The water refreezes and expands, prying the rock
apart
 As the glacier moves across the fractured surface it
incorporates blocks of rock into its ice
o Abrasion
 As glacial ice and rock fragments move over bedrock,
it works like sandpaper to smooth out the surface
below
 By the glacial gristmill, pulverized rock is produced
called rock flour
 So much of this produced that the meltwater leaving
the glacier has a grayish appearance
o Four Factors of Erosion
Rate of glacial movement
Thickness of ice
Shape, abundance, and hardness of rock fragments in
the ice at the base of the glacier
 Type of surface below the glacier
Landforms created by Glacial Erosion (Olivia & Ja’Reighyah)
o Glaciers are responsible for a variety of landscapes
o Erosion by glaciers produce many features in mountainous
areas
o Glaciated Valleys
 Prior to glaciation alpine valleys were V-shaped due to
downcutting of streams
 Glaciers widen, deepen, and straightens valleys,
changing the V-shape to a U-shaped valley
 U-shaped valleys are called Glacial Troughs
o Cirques
 A bowl shaped depression at the head of a glacial
valley
 Surrounded on 3 sides by steep rock walls, which are
the focal point of the glacier’s growth
 Glaciers carry away Cirques acting as a conveyer belt
to move debris
o Arêtes and Horns
 Arêtes – snaking sharp edged ridges
 Horns – sharp pyramid like peaks
 Horns form around cirques on the sides of mountains
 Arêtes form on opposite sides of a divide from a
cirque
Glacial Deposit (Chance & Paxton)
o Glaciers transport huge loads of debris as they slowly
advance across the land leaving sediment as it melts
o There are 2 types of glacial drifts: Till & Stratified Drift
o Till Deposits
 Deposited directly by glaciers
 Ice cannot sort the sediment it carries
 Those deposits are normally unsorted mixtures of
different particle sizes
o Stratified Drift
 Sorted by size & weight of the debris





Some deposits of drift are sorted by size and weight of
the debris
 Stratified drift is made mainly of sand and gravel
Moraines, Outwash Plains, & Kettles (Caitlin C, Sierra, & Tristan)
(Evan, Hannah, & Nick)
o Lateral Moraines
 Ridges that form long the side of glacial valleys when a
glacier melts and leaves gathered materials
 Medial moraines form when 2 valley glaciers join to
make a ice stream
o End Moraines & Ground Moraines
 Ground moraines form when glaciers began to
withdraw
 Form gently rolling plains instead of ridges
 End moraines formed from debris caused by melted ice
 The longer the glacier remains stationary, the
larger the end moraine grows
o Terminal & Recessional Moraines
 Remain stationary for a short period of time
 Repeats many times before glacier completely melts
o Outwash Plains
 Water flowing from the glacier containing fine
sediment slows down and drops sediment in ramp like
structures called outwash plain
 Downstream from the end moraines
o Kettles
 Depressions in small lakes
 Form when a big block of ice gets buried in a drift and
melts
 Melting leaves glacier sediment with pits
o Drumlins & Eskers
 Eskers are snake like ridge made of sand and gravel
from streams that flowed through glaciers
 Drumlins are a landform made from tills of glaciers
they are steep on the side and can be as tall as 60 m
Glaciers of the Ice Age (Makayla & John)
o Glaciers covered almost 30 % of Earth’s land
o Most recent ice age was 2-3 million years ago





o Many major glacial episodes occurred during Pleistocene
Period
o Glaciers store 75% of earth’s freshwater
Geologic Processes in Arid Climates (Kaitlyn & Juston)
o Arid climates are hot & dry & have sharp rocks and steep
canyons
o Covered in dust and pebbles
o Weathering
 Weathered debris in a desert is the result of
mechanical weathering
 Chemical weathering does not happen as often
because there is a lack of acidic organic material
o Role of Water
 There are always riverbeds in the desert, but most of
the time they are dried up
 These channels carry water when it rains which is rare
 Flash flooding in the desert is common when it rains,
but the water is gone quickly because the soil does not
soak it up
Basin / Range: A Desert Landscape (Claire & Will)
o Playa Lake
o Alluvial Fan
o Water in the Desert
 Arid / Desert regions generally lack permanent streams
and complex drainage systems because desert streams
are usually evaporated or they seep in the soil through
infiltration long before they can ever reach the sea
 Most desert erosion is the result of running water, not
wind erosion
o Exceptions
 When most dry out some streams or rivers like the Nile
in NE Africa manage to flow through the heat
 Loss of energy results in the release of the majority of
the eroded material which creates alluvial fans
 Playa Lakes form because of heavy precipitation, are
even rarer
 Playa lakes are thin lakes that do not exist for a long
 They form on the basin’s floor after possibly flowing
across alluvial fans
The bed of the lake that is left after it dries up is
called a playa
Wind Erosion (David & Karlee)
o About Wind Erosion
 Wind erodes in the desert by deflation & abrasion
 Deflation – lifting and removal of loose particles
 Abrasion – the process of scraping or wearing away
 Ex) Dust Bowl
Wind Deposits (Miceala & AJ)
o Wind creates landform by depositing sediment
o Loess & sand dunes are landscape features deposited by wind
o Loess
 Windblown silt that blankets the landscape
 Dust storms pick up the material, transport it, then
deposit it
o Sand Dunes
 Wind releases its load of sediment when velocity
(speed) falls and the energy available to move lessens
 Sand accumulates when obstruction crosses its path
and slows its movement
 Dunes occur when the wind encounters an
obstruction and the velocity (speed) falls and the sand
particles fall
 Dunes are usually more steeper on sheltered side and
more of a gentle slope on the side of the wind
 Cross beds happen when sand is deposited on the
sheltered side of the dune, creating layers inclined in
the direction wind is blowing
Types of Sand Dunes (Conner & Courtney)
o Form when wind deposits sand in mounds and ridges
o Can occur in places where the wind encounters and
obstruction
o 6 different types of sand dunes
o Transverse Dunes
 Ridges are perpendicular to the wind direction
 Typically found in coastal areas
o Star Dunes
 Form when the area has a complex wind regime, where
the wind blows in various directions




o
o
o
o
o
 Star dunes will have at least 3 or more arms
Barchanoid Dunes
 Common dune
 Form at right angles
Longitudinal Dunes
 Long ridges of sand that are parallel to the wind
 Occur where sand supplies are moderate
Parabolic Dunes
 Sand sheet is covered in vegetation
 When wind pushes the sand in a forward motion, it
moves
Barchan Dunes
 Solitary sand dunes shaped like a crescent
 These form on flat, hard grounds
 They reach heights of about 30 ft.