EESA06H3 Chapter Notes - Chapter 16: Pluvial, Moraine, Rockfall
10 May 2018
School
Department
Course
Professor
Ch.16 – Glaciers, Glaciation and Permafrost
- Climate changes during glacial ages altered landscapes
- More land was above sea level as glaciers were frozen sea water
- Ended 10,000 years ago
- Evidence of older glaciations preserved in rocks
- As far back as 2.8 billion years
- Principle of uniformitarianism must be applied to the study of glaciation
Glacier: a large, long-lasting mass of ice, formed on land, that moves downslope
under the influence of gravity
- Develops as snow is compacted and recrystallized
- Can develop anywhere
- More snow accumulates than melts
- Two types of glaciated terrain
Alpine Glaciation: found in mountainous regions
Continental Glaciation: exists where a large part of a continent (thousands of square
kilometres) is covered by glacial ice
- Both change the landscape
- Louis Agassiz a Swiss naturalist in the 1800s
Theory of Glacial Ages: at times in the past, colder climates prevailed during which
much more of the land surface of Earth was glaciated than at present
- Lakes are products of deep erosion by past glaciations
- Fertile soil developed on loose debris transported and deposited by glaciers
- Some glacial deposits contain mineral indicators used to locate rich sources
- Deposits of glacial sediment store and transmit groundwater
- Glaciers occur both in cold, polar regions, where there is little melting during the
summer, and in temperate climates that have heavy snowfall during the winter
months
- Found where more snow falls during the cold time of year than can be melted during
warm months
- 2% of Canada covered by glaciers
- Glaciers are common near the equator
- Colder temperatures at higher altitudes
- Glaciation is most extensive in polar regions, where little melting takes place at any
time of year
- 85 percent of the present-day glacier ice is on the Antarctic continent
- Stores most of Earth’s fresh water in the form of ice
Valley Glacier: a glacier that is confined to a valley and flows from a higher to a
lower elevation
- Like streams, small valley glaciers may be tributaries to a larger trunk system
- Prevalent in areas of alpine glaciation
- Most glaciers in Canada and the United States, being in mountains, are of the valley
type
Ice Sheet: a mass of ice that is not restricted to a valley but covers a large area of
land (more than 50,000 square kilometres)
- Associated with continental glaciation
- Greenland and Antarctica, only two places with ice sheets
Ice Cap: similar to ice sheets but smaller body
- Both flow downward and outward from a central high point
- Firn compacted mass of granular snow, transitional between snow and glacier ice
- Glacial Ice granules forced together
- Glacier ice moves downward due to gravity
Ablated: removal through melting or other means
- Some evaporate directly
- Calve breaking off of ice blocks
Ice Bergs: floating blocks of ice
- When moving glacier meets body of water
- Glacial Budget is positive if gains more snow than loses
- Will expand
- If opposite then negative melt
Advancing Glaciers: glaciers with positive budgets push outward and downward at
their edges
Receding Glaciers: negative budgets grow smaller and their edges melt back
- Glacial ice moves down-valley regardless of budget
- There can be balanced budget, melting equals freezing
Zone of Accumulation: upper part of a glacier with a perennial snow cover
Zone of Ablation: lower part where ice is lost, or ab- lated, by melting, evaporation,
and calving
Equilibrium Line: boundary between these two altitudinal zones of a glacier which
marks the highest point at which the glacier’s winter snow cover is lost during a melt
season
- May shift up or down from year to year
- Depends on whether accumulation of ablation is greater
- Indicates positive or negative budget
- Upward line then negative budget
- Downward line then positive budget
- Balanced if not movig
Terminus: lower edge of a glacier
- Moves down-valley when valley glacier has positive budget
- Opposite if negative budget
Document Summary
Climate changes during glacial ages altered landscapes. More land was above sea level as glaciers were frozen sea water. Evidence of older glaciations preserved in rocks. As far back as 2. 8 billion years. Principle of uniformitarianism must be applied to the study of glaciation. Glacier: a large, long-lasting mass of ice, formed on land, that moves downslope under the influence of gravity. Develops as snow is compacted and recrystallized. Continental glaciation: exists where a large part of a continent (thousands of square kilometres) is covered by glacial ice. Louis agassiz a swiss naturalist in the 1800s. Theory of glacial ages: at times in the past, colder climates prevailed during which much more of the land surface of earth was glaciated than at present. Lakes are products of deep erosion by past glaciations. Fertile soil developed on loose debris transported and deposited by glaciers. Some glacial deposits contain mineral indicators used to locate rich sources.
