4 Formation of glacial ice 3. 5 Formation of glacial ice (cont.) 3. 6 Glacier economy and general flow structure 4

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1 Contents 1 Glacier Flow 2 2 Definition 2 3 Amount 3 4 Formation of glacial ice 3 5 Formation of glacial ice (cont.) 3 6 Glacier economy and general flow structure 4 7 Example 5 8 Examples 6 9 Ice movement 6 10 Rheology and velocity structure 7 11 Glacial Geology 7 12 Glacier Flow Pattern 8 13 Cross section 8 14 Glacial features close-up 9 15 Glacial features 9 16 Glaciers on Middle Earth Glacial Landforms Deposits Deposits and Landforms 12 1

2 1 Glacier Flow Dunes Glacier Sea or Lake Slide River Mountains Plains In areas with high mountains or at high latitude, there is an additional sediment transport and land forming process - flowing ice. Generally acts on sediments early in erosion cycle, as streams often originate from ice. 2 Definition Glacier an ice mass originating on land from accumulation, compaction and recrystallization of snow. It must show evidence of past or present movement. There are two main types Alpine glaciers small glaciers originating in mountain valleys Continental glaciers ice sheets covering large portions of a land mass 2

3 Amount About 10% of the land surface is covered by glaciers Most of the fresh water on earth is in glaciers 4 Formation of glacial ice Snow falls and accumulates Pressure melting of snow crystal.

3 3 Amount About 10% of the land surface is covered by glaciers Most of the fresh water on earth is in glaciers 4 Formation of glacial ice Snow falls and accumulates Pressure melting of snow crystal. Huge pressures at junctions of snowflakes causes melting, sublimation condensation in low pressure areas away from contact points 5 Formation of glacial ice (cont.) Crystals become more closely packed firn (after 1 year) 3

4 Structure of snow and firn from CRREL. All interconnections in air passageways are sealed off ice. 6 Glacier economy and general flow structure Accumulation zone that part of the glacier in which new snow and ice are added during one year Ablation zone that part of the glacier in which there is net snow and ice removal during year Glaciers can also calve into water bodies 4

5 Mass balance the net accumulation over the course of a year (usually Sept to Sept) Accumulation zone and ablation zone are separated by the snow line 7 Example 5

Oblique aerial photograph looking east at several of the glaciers on Puncak Jaya in 1936. Left to right: Northwall Firn, Meren Glacier, and Carstensz Glacier. Photograph no. S.136 by J.J. Dozy.

6 Oblique aerial photograph looking east at several of the glaciers on Puncak Jaya in Left to right: Northwall Firn, Meren Glacier, and Carstensz Glacier. Photograph no. S.136 by J.J. Dozy. From USGS. 8 Examples More views ELA Exit Glacier ELA Peyto Glacier Schematic (and image database) 9 Ice movement Plastic flow fluid-like flow below 50 m, where pressure is high Flow has two components, internal deformation and basal slip Zone of fracture that part of a glacier shallower than 50 m 6

7 The zone of fracture is dominated crevasses and seracs The rate of movement can be so slow that trees grow on sediments or fast, up to about 100 m/day in a surge 10 Rheology and velocity structure Velocity structure in a river Linear (Newtonian) fluid, generally turbulent Velocity structure in ice Non-Newtonian fluid, laminar Plastic - yield stress Flow visualization 11 Glacial Geology Glacial geology is the term for the investigation of the deposits and landforms left by glaciers Given the large areas of the continents covered by glacial deposits, this is a major branch of geology especially important to the understanding of nearsurface groundwater bodies and pollution 7

8 12 Glacier Flow Pattern 13 Cross section 8

9 14 Glacial features close-up 15 Glacial features 9

10 16 Glaciers on Middle Earth 10

11 17 Glacial Landforms Two types: erosional, depositional NOAA image database Image database (offsite) Satellite imagery (offsite) Airphotos: Long s Peak (stereogram 502) 18 Deposits Diamicton any massive bedded, poorly sorted deposit. Origins arevaried and can include many mass wasting and glacial processes. Drift deposits directly from ice or from water in contact with ice There are two kinds of drift Till massive bedded, poorly sorted, deposited directly from ice Stratified drift stratified, sorted, deposited from ice-contact water 11

12 19 Deposits and Landforms Till in moraine, drumlin (ablation tills), ground moraine (lodgement till). unstratified, poorly sorted, striated stones, erratic provenance. Stratified drift (glaciofluvial and glaciolacustrine) in kame terrace, valley train, outwash plain, esker (glaciofluvial), varves (glaciolacustrine). Stratified, sorted, dropstones. Glacioaeolian In loess plateaus. Unstratified, fine grained. 12

Glaciers. (Shaping Earth s Surface, Part 6) Science 330 Summer 2005

Glaciers. (Shaping Earth s Surface, Part 6) Science 330 Summer 2005 Glaciers (Shaping Earth s Surface, Part 6) Science 330 Summer 2005 1 Glaciers Glaciers are parts of two basic cycles Hydrologic cycle Rock cycle Glacier a thick mass of ice that originates on land from