UNIVERSITY OF SOUTH ALABAMA
Last Time
Groundwater
•
GY 301: Geomorphology
•
The hydrosphere and the hydrological cycle
•
Groundwater concepts
Hydrogeology concepts (Darcy’s Law, 3 point problems)
Lecture 21:
Glaciers and Glacial
Mechanics
Source: Erebus_glacier_cave_NOAA_1978.jpg
Groundwater
Hydrological Cycle
Groundwater is water that infiltrates below the Earth’s surface
Most of the planet’s
water is in the oceans
(96%) followed by the
ice caps (3%) and then
groundwater (1%)
Porosity: percent void
space in a material
Permeability: degree of
connectivity of pores
(ability of a material to
transmit a fluid)
http://www.coloradocollege.edu/dept/ev/courses/EV211WWW/hydrological%20cycle.jpg
http://www.belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/permeability.gif
Water Table Morphology
• Porous layers that are capable of passing water and releasing it
at springs and/or wells are called aquifers.
Types of Aquifers
Potentiometric Surface:
elevation to which
the pressurized water
in a confined aquifer
will rise
Artesian Well: water
rises to an elevation
above the aquifer
Flowing Artesian
Well/Spring:
potentiometric
surface is above the
ground surface
http://www.douglas.co.us/water/images/Denver_Basin_Aquifers_clip_image004.jpg
http://www.tol.ca/files/web_images/engineering/environment/WebImages/unconfined.jpg
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Other Groundwater Issues
• Ground subsidence and collapse
Sinkholes
Groundwater Flow
• Darcy’s Law: governs the
volume of groundwater
produced at a well head
Q= A(K x h)
l
– Q is volume
– A is cross sectional area of
aquifer
– K is permeability
– h is hydraulic head
i.e., you can determine groundwater flow rates
– l is map distance
Groundwater Flow
Three Point Problem
Today’s Lecture
Glaciers and Glacial Mechanics
•
Calculate the direction of
groundwater flow based upon
water table elevations
•
Types of glaciers
Formation of glacial ice
•
Movement of ice
Water flows from high elevations to
low elevations
http://www.uwgb.edu/dutchs/Graphics-Geol/structur/manual/fig13a.gif
Glaciers
Glaciers
Glaciers are thick masses of ice that originate on land through
the accumulation of snow.
Glaciers are thick masses of ice that originate on land through
the accumulation of snow.
Glaciers form through a 3
step process
All that is required is
for more snow to fall
in the cold winter
months than melts in
the warm summer
months.
Snow
Firn
Glacial Ice
http://media-cdn.tripadvisor.com/media/photo-s/01/25/4a/ee/in-the-mountains-above.jpg
http://www.ig.utexas.edu
2
Glaciers
Glaciers
Glaciers are thick masses of ice that originate on land through
the accumulation of snow.
Glaciers are thick masses of ice that originate on land through
the accumulation of snow.
Glaciers form through a 3
step process
Glaciers form through a 3
step process
Snow
Snow
Firn
Firn
Glacial Ice
Glacial Ice
http://pubs.usgs.gov/of/2004/1216/f/images/firn1.gif
http://www.swisseduc.ch/glaciers/glossary/icons/firn.jpg
Glaciers
Types of Glaciers
The transition from
snow to ice results in
an increase in density
and a loss of porosity.
Glaciers form in environments where it is cold.
1) Polar regions: Ice Caps and Continental Glaciers
2) High altitude (e.g., >10,000 feet): Alpine or Valley Glaciers
http://eesc.ldeo.columbia.edu
Types of Glaciers
Alpine Glaciers
Alpine or Valley Glaciers
(frozen rivers)
(Zone of Accumulation; Zone of Wasting/Ablation, Calving,)
http://www.scienceclarified.com/images/uesc_05_img0282.jpg
Alpine or Valley Glaciers
http://www.scienceclarified.com/images/uesc_05_img0282.jpg
http://stloe.most.go.th/html/lo_index/LOcanada3/305/images/5_2.jpg
Chalk Board
3
Alpine Glaciers
Alpine Glaciers
Components of Alpine Glaciers
•Toe
•Head
•Compression Ridges
•Crevasses
Components of Alpine Glaciers
•Toe
•Head
•Compression Ridges
•Crevasses
Head
http://www.geo.mtu.edu/great_lakes/ice/field_photos/images/pressure_ridge3.jpg
Toe
http://www.scienceclarified.com/images/uesc_05_img0282.jpg
http://www.ig.utexas.edu
http://stloe.most.go.th/html/lo_index/LOcanada3/305/images/5_2.jpg
http://farm1.static.flickr.com/91/266492544_90908ec6c0_o.jpg
Alpine Glaciers
http://www.ig.utexas.edu
Ice Movement
Components of Alpine Glaciers
•Toe
•Head
•Compression Ridges
•Crevasses
Ice moves down slope
from the zone of
accumulation to the
zone of ablation due to a
combination of plastic
flow and basal slip.
http://cascadeclimbers.com/plab/data/509/3820Dorado0002.JPG
http://www.ig.utexas.edu
http://nevis.k12.mn.us/academics/science/glacier_hor_profile1.jpg
Ice Movement
Ice moves down slope
from the zone of
accumulation to the
zone of ablation due to a
combination of plastic
flow and basal slip.
Ice Movement
Firn
50 m
Ice moves down slope
from the zone of
accumulation to the
zone of ablation due to a
combination of plastic
flow and basal slip.
Firn
Flow
50 m
Slip
4
Ice Movement
Ice Movement
Ice moves down slope
from the zone of
accumulation to the
zone of ablation due to a
combination of plastic
flow and basal slip.
Ice advances down hill due to
basal slip and plastic flow, but
glaciers can appear to retreat if
the rate of melting exceeds the
rate of down slope movement.
Firn
Flow
50 m
Rhone Glacier
http://media.photobucket.com
Glacial Budget
Equilibrium line: the boundary between accumulation and
ablation on a glacier.
Geological Effects of Glaciers
Ice exerts
tremendous erosive
force on bedrock
forming unique
geomorphologic
features and
transporting great
quantities of
sediment ….
… to be continued
http://www.kschapterc.org/album-mead/23.jpg
Upcoming Stuff
Homework
Groundwater and Karst Geomorphology (due Friday)
Next Lecture:
Alpine Glacier Geomorphology
Friday’s Lab:
Map interpretation (alpine glaciers)
Soup Day
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