Observing Snow - Glacier Slide Show

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Glacier Slide Show

In order to tap into a variety of learning styles the glacier information is organized into a slide lecture including not only photographs, but maps, graphs, and scientific illustrations. The last few slides are of the Peter's Glacier, used in the next exercise to teach map skills and to calculate its flow rate during the 1986-87 surging episode.

This activity is presented with special thanks to Dennis Trabant from the USGS Water Resources Division and Keith Echelmeyer from the UAF Geophysical Institute for providing slides, aerials photos, and lots of ideas and information.

Peter's Glacier
Slide #1

The Peter's Glacier is a good example of a mountain glacier located in Denali National Park in interior Alaska.

Columbia Glacier
Slide #2

The Columbia Glacier is an excellent example of a tide water glacier located in Prince William Sound, Alaska. A tidewater glacier has a terminus in the ocean.

A close up of the Columbia's tidewater glacier
Slide #3

A close up of the Columbia's tidewater glacier terminus in the ocean.

A hanging glacier terminus with a researcher standing under the cliff-like terminus
Slide #4

A hanging glacier terminus with a researcher standing under the cliff-like terminus. Glaciers that are advancing rapidly often have moraines with abrupt faces full of poorly sorted glacial till that has been pushed forward by the glacier.

Glacial till
Slide #5

Glacial till. Poorly sorted rock material that has been eroded and deposited by the movement of a glacier.

Bed rock smoothed and scratched by glacial movement
Slide #6

Bed rock smoothed and scratched by glacial movement. Lines, striations, and scratches in the rock are created by the abrasion of glacier movement. The resulting fine glacial flour is produced much like sandpaper smoothing and creating dust.

Two rivers merging
Slide #7

Two rivers merging: one river is clear and the other is of glacial origin and laden with glacial silt. The difference in river clarity is very evident.

important glacial features
Slide #8

A diagram from, "Glaciers of North America" by Sue Ferguson. It shows important glacial features.

  • Identify and explain: Medial Moraine, Lateral Moraine, Zone of Ablation

Normal Mountain Glacier
Slide #9

A Normal Mountain Glacier. This glacier flows at a relatively normal rate of about 100 meters / year. The medial moraines are parallel and regular.

The terminus of Susitna Glacier during the 1985 surge event
Slide #10

The terminus of Susitna Glacier during the 1985 surge event.

  • Identify: Flowing water from under the glacier, Flowing water along the sides of the glacier, Flowing water seeping out of gravels, Folded moraines, Dirty terminus, Kettle ponds in moraine.
  • What phases of water can you see in this slide?

SOLID, LIQUID, & VAPOR. Clouds, glacial ice, snow, ponds, and streams are all examples of the many phases of water in the hydrologic cycle represented in this photo.

An average valley glacier in North America travels about 30 cm (12 in.) each day
Slide # 11

A diagram from "Glaciers of North America," by Sue Ferguson. An average valley glacier in North America travels about 30 cm (12 in.) each day near its surface and glides along its belly at about 10 cm (4 in.) each day.

  • Why would a glacier move more slowly at the bottom than
    the top?

FRICTION caused by valley bottom.

The middle of a glacier usually travels faster than the edges
Slide # 12

A diagram from "Glaciers of North America," by Sue Ferguson. The middle of a glacier usually travels faster than the edges due to FRICTION of the ice passing over rock.

medial moraine
Slide # 13

A medial moraine is created by the flow of ice in different rates in different places. These differences create currents or "waves" in the flow of the ice that push up and deposit rock material. Those deposits located in the center of a glacier or where two valley glaciers merge are the medial moraines.

terminus of the Gulkana Glacier
Slide # 14

The terminus of the Gulkana Glacier located east of the Richardson Highway near Summit Lake.
The Gulkana is a retreating glacier, note the zone of ablation at end of glacier where rock and dirt have been deposited.

Ice Fall on the Peter's Glacier
Slide # 15

An Ice Fall on the Peter's Glacier. The ice flows over such steep terrain that it acts like a frozen water fall. The ice moves so quickly that it breaks rather than flowing by deformation. This is a good example of Brittle Deformation.

  • What kind of deformation do surging glaciers experience during a surge? Brittle.

Comparing a glacier's accumulation area
Slide # 16

A diagram from "Glaciers of North America," by Sue Ferguson. Comparing a glacier's accumulation area with its total area gives an estimate of its health. The boundary between the accumulation zone and ablation zone is called the equilibrium line.

A black and white photo of two glaciers side by side
Slide # 17

A black and white photo of two glaciers side by side in two adjacent valleys.

· Which glacier is advancing?

The glacier on the left is advancing. Note that the terminus is more "bulbus". The glacier on the right is retreating. Note that it looks deflated.

Surging Susitna Glacier
Slide # 18

The Surging Susitna Glacier. Some distinctive features of a surging glacier are looped moraines.

  • Compared to a normal glacier, what is different about this glacier that causes its moraines to occur in such interesting patterns? There is a reduced amount of friction where the glacier contacts the valley bottom and sides. This lubrication causes the ice flow rate to accelerate dramatically.

When a glacier surges it can move ten to one hundred times faster than its normal rate of motion
Slide # 19

A diagram from "Glaciers of North America," by Sue Ferguson. When a glacier surges it can move ten to one hundred times faster than its normal rate of motion. This could cause a glacier, which normally moves the length of a football field in one year, to move the same distance in one day.

A color diagram illustrating the cross section of a surging glacier
Slide # 20

A color diagram illustrating the cross section of a surging glacier positioned on top of a layer of subglacial water in bedrock. A glacier surges because it's plumbing becomes clogged. Water becomes trapped under the glacier reducing friction and causing sudden, rapid advances. Glaciers surge in cycles. Surging glaciers in the Alaska Range are estimated to surge every 50-75 years. Note lateral and medial moraines, parallel to valley walls.

The bathtub photo
Slide # 21

The bathtub photo. Once the glacier surges, mass moves down valley. The bathtub ring shows what the surface elevation of the glacier was prior to the surge in the upper portions of the glacier.

Susitna Glacier
Slide # 22

The Susitna Glacier located off the Denali Highway in interior Alaska.

· Is this a surging glacier? Yes
· How can you tell? Looped, or contorted moraines.

news paper tabloid with the headlines, "Ocean Rising 150 Ft."
Slide # 23

A news paper tabloid with the headlines, "Ocean Rising 150 Ft." along with a picture of the Statue of Liberty chest deep in water. An article follows the headlines, "Summer Heat Wave Will Melt Polar Ice Caps and Result in Ocean Rising 150 Ft. and Flooding Coastal Areas. Will your City Survive?"

· Why do we study glaciers? To understand long - term climate trends.

map of the extent of glaciation
Slide # 24

A map of the extent of glaciation during the most recent episodic ice age events that dated from 160,000 to 15,000 years ago. Note regions which were covered by glaciers during the last ice age and areas that are currently covered in glaciers.

This photo consists of three main instruments used to collect data from a glacier.
Slide # 25

This photo consists of three main instruments used to collect data from a glacier. The antenna is part of a satellite telemetry system which transmits data back to researchers at the Geophysical Institute Fairbanks, Alaska, via satellite. The anometer on top of the pole measures wind speed, and the wooden box on the stand contains a temperature sensor. There is a slit opening in front of the box which allows the sun to strike the sensor only once a day causing a temperature reading to rise for a short time. Researchers "calibrate" their electronic clock in the more modern data collection system using the daily temperature spike.

Researchers use snowmachines to travel
Slide # 26

Researchers use snowmachines to travel to where they can study glaciers. Two researchers are out on an ice field as the snow machine pulls a sled loaded with equipment.

A Geology research camp
Slide # 27

A Geology research camp with equipment outside a shelter.

A researcher (woman) walking on a glacier
Slide # 28

A researcher (woman) walking on a glacier, stepping over a crevasse. She is holding an ice axe and carrying a backpack. This photo highlights the dangers associated with work on a glacier and the need for good equipment and special training prior to going out in the field. Always use caution when out on glaciers!

A crevasse on a glacier with researchers and equipment in the background.
Slide # 29

A crevasse on a glacier with researchers and equipment in the background. The researcher appears to be surveying in the background. Periodic surveys determine a glacier's net accumulation of snow, and help determine the overall water budget for a given watershed.

An exposed wall with a person standing nearby
Slide # 30

An exposed wall with a person standing nearby observing the snow profile visible in the wall.

A deep snow pit dug into a glacier.
Slide # 31

A deep snow pit dug into a glacier. A researcher is looking down into the snow pit. The different layers are visible. There is a small trench cut into the side of the snow pit where researchers have collected snow density data using a snow density sampling box. This is the same instrument we use in our Snow Pit Activity to take samples to determine snow density.

A close up of the snow pit
Slide # 32

A close up of the snow pit with the researcher down at the bottom of the deep pit using a snow density sampling box.

Close up of the inside of the snow pit
Slide # 33

Close up of the inside of the snow pit with a meter stick measuring the height of each layer. You can also see the thermometer dials in the lower left of the photo.

A sketch of the glaciologists' snow pit profile.
Slide # 34

A sketch of the glaciologists' snow pit profile. The sketch includes the height, density, and temperature of each layer. In addition, each layer is coded as to the type of snow present in the layer. Snow types they have observed include: wind slab, fine snow, fresh snow, depth hoar, and ice layers. We will record the snow layer we encounter in the Snow Pit Activity.

A McGrath student taking temperature measurements in a snow pit.
Slide # 35

A McGrath student taking temperature measurements in a snow pit. The colored sticks are the tongue depressors, where the different snow layers have been identified and marked.

A McGrath student using the density sampling box
Slide # 36

A McGrath student using the density sampling box, a tool that samples precisely 2003cm of snow. The sample is then weighed. The information is used to calculate the density, or percentage of water, of the snow layer.

A close up photo of a stellar snow
Slide # 37

A close up photo of a stellar snow crystal by Edward LaChapelle.

the processes of Destructive Metamorphism, Pressure and the Melt Freeze cycle
Slide # 38

A diagram from "Glaciers of North America," by Sue Ferguson. Through the processes of Destructive Metamorphism, Pressure and the Melt Freeze cycle, delicate snow crystals are transformed into rounded ice grains. Through time, they sinter together to form larger and larger ice crystals, eventually becoming glacier ice. Ice crystals grow dramatically as they transform from snowflakes to firn, and ultimately into glacial ice.

A photo of glacier ice crystals
Slide # 39

A photo of glacier ice crystals. The measuring tape reads inches.

· How big is the largest crystal?

A close up of a researcher down in a snow pit examining glacier ice crystals.
Slide # 40

A close up of a researcher down in a snow pit examining glacier ice crystals.

A close up of the same researcher photographing glacier ice crystals.
Slide # 41

A close up of the same researcher photographing glacier ice crystals.

A close up of ink dyed glacier ice crystals.
Slide # 42

A close up of ink dyed glacier ice crystals.

  • Why do you think the spots (air bubbles) are oval shaped? Pressure from the ice mass and its movement. The long axis of the bubbles are perpendicular to direction of greatest force.

Peters Glacier
Slide # 43

A photo looking down on the margin of the Peters Glacier during the initial phases of a surge. Ice is part of the glacier surface, the black rock is the valley wall, and the gray is water.

  • Why is the water gray? Contains silt
  • Why would the water contain silt? Source is the bottom of the glacier.

Peter's Glacier
Slide # 44

Looking down the Peter's Glacier.

The edge of the Peter's Glacier during surge
Slide # 45

The edge of the Peter's Glacier during surge.

  • By looking at the ice, can you tell if deformation was brittle or ductile? Yes, brittle.

A close up of the Peter's Glacier terminus.
Slide # 46

A close up of the Peter's Glacier terminus.

A close up of the Peter's Glacier terminus.
Slide # 47

A close up of the Peter's Glacier terminus.

Peter's Glacier
Slide # 48

A view from an airplane of the Peter's Glacier.

Researchers building rock karins
Slide # 49

Researchers building rock karins in 100' intervals in front of the Peters Glacier during the surge. They retreat to a safe place and time how long it takes for the surging glacier to run over the regularly placed rock karins. From the information gathered the rate of the surging glacier can be determined.
Rate = Distance/Time.

Peter's Glacier PRE-SURGE
Slide # 50

The first of the series: Peter's Glacier PRE-SURGE, a red line indicates the terminus.

Peter's Glacier PRE-SURGE
Slide # 51

The second of the series: Peter's Glacier, POST - SURGE, the red line indicates the terminus.

Peter's Glacier PRE-SURGE
Slide # 52

The third of the series: The Peter's Glacier POST - SURGE, a different view.

Back to Glaciers

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