The Recent Ice Age
Why is the sea continuing to rise?
Jay Ingram – glaciers continue to melt – the last ice age continues to exert
effect over the landscape.
Eastern Canada – looked like this – covered with mountains and ice.
Shaping of valleys – much of what we take for granted.
Ice sheets – key role in soil, other materials left for forest growth. Groundwater
– by sand left from the glaciers when they retreated. Where we build our roads,
where our cities are located. When you lie on the beach – it’s there b/c of an ice
age which is still being felt today.
There have been many ice ages. 2.5 million years ago. The last ice age – 20,000
years ago – Atlantic Canada was covered by ice. Clearing about 10,000 years ago.
Visual reminder during the recent ice age. A major journey from Montreal – snow
and ice – NE coast of Baffin Island. Glacial processes can be studied here. Pond
Inlet.
Pond Inlet - 600km above the Arctic Circle. July avg temp 8 degrees. Fishing
and hunting for their lively hood. North Baffin inlet. The ice ages since the 2.5
million years have changed the face of the arctic. The ice originated from snow
fall. It was compressed under its own weight. Ice sheets are forced outwards
from its own weight. Ice front retreats when melting is more rapid.
Atlantic geocenter in Dartmouth NS. How glaciation works and how it’s affecting
us.
Ice sheets – high cliffs of ice from NS to Baffin Island. Ice split and flow down
valleys as glaciers. Freezing and thawing causes erosion. Fjord – when the area is
flooded. Ice melts at the age of an ice sheet. Melt water streams. Building out
a delta into the fjord.
Scientists – sand deposits – sequence of events during an ice age. Animals that
occupy have been dated for millions of years by radio carbon dating. Geologists
can then piece together a history of an entire ice age.
Raised ridges –
Ice sheets – lots of activity inside them – full of water water flows through
tunnels in the ice with gravel and sand as the ice melts it dumps – eskers –
Maritimes – sand and gravel – high quality – used in building and highway
constructions.
Moraine – dumped at front as a mound – valley glacier on Baffin island –
Areas such as Atlantic Provinces – bold resurface as seen in Yarmouth Nova
Scotia.
Delta’s when they reach the sea.
Parrsboro – formed on a delta – aquifer for the towns wells.
Glaciated areas – eastern and south shore. Lunenburg – built on a landform left
Drumlin – deposited by advancing glaciers but since then have been eroded by the
sea.
How have geologists pieced together – bare outcrops – NFLD – large grooves –
rocks at the base of the ice sheet being dragged over the ice sheet?
Differences in ice flow in different times. More information – deposits of
Till – 2 types of till – grey till –local area, red till – over 100km away – from
glaciers from far away.
St. John River NB – before glaciers 5km different course and then the glaciers
forced the river to find a different outlet.
Age of shells – 13, 000 years – ice retreated from the area. (Radio carbon
dating).
What’s happened in the 10,000 years since?
The revegetation – tree growth.
Sediments at the bottom of lakes (like tree growth). Looking for clues in the
mud looking at the ice age time table.
Lab analysis – 9000 years ago – spruce and fir trees started 8500 years ago.
Why does the earth go through these fluctuations?
They have occurred numerous times. Almost regular climate and glaciation.
Ice ages – small changes in the earth’s orbit. Advance and retreat of ice sheets.
It seems like 20,000 doesn’t effect us – one important effect that is still going
on today – ice sheets – volume of frozen water – ice sheets built up on land and
the sea level dropped, earth’s crust was depressed – ice melts back – rebound is
still occurring.
Cape chignecto – raised beach – 30m above water it was once sea level but had to
retreat back because it bounced back.
Beach in Antigonish –
Sea level rose – (tape quality poor here).
Weight of glaciers – topography of the Atlantic coast – east coast fishing banks –
sea gradually drowned these banks.
Sea level continues to rise in atl. Canada. People move closer to the ocean every
year.
Sea level is gradually
3mm per year (in and around Halifax). Since the founding of Halifax – 1m!
Halifax harbour – didn’t
Fresh Water Lake and narrow river outlet and sea level rose forcing the narrow
river to become wider. The lake is now Bedford basin. Remains of organisms that
only lived in fresh water. 6000 years before present. The atl ocean drowned the
lake 6000 years ago.
Much of the coast line – being pushed back by erosion as sea level rises.
Chetezetcook – narrow ridge of gravel – and could disappear all together – it’s
just a strip of gravel.
Rocks and sand of the drumlin – rocks and sand of the beach from here.
Erosion – unstable hill – it will be almost completely gone. (Joggins as well).
Ice sheets return more water to the sea – the rising sea level effects:
Landscape, lively hood of many communities (then it would be flooded),
Extent of the land that the farm used to exist – it was over taken by the sea. He
had to move inland and start again. Where I was born is out in the ocean now.
Grandfather’s well – it’s out in the ocean.
Ice age 20,000 years ago – advance and retreat of the ice – effected our
environment. Direct result as the deposits left by melting ice sheets. Soils
better fro forestry or agriculture. Landscapes and harbours are shaped by ice
sheets and where we put our communities. Economic – sand and gravel and water
supply. Materials left by the ice sheets – have formed our beaches. Our coast
line will continue to retreat.
Last ice age and the next one. 23,000 years in the future – might be another ice
age in atl. Canada.