GEOGRAPHY SECOND PART
GLACIATION
•Louis Agassiz from
Switzerland
•French-speaking, so
most names are French
•“Glace” is French for
ice (crème glace)
•‘Glass’ is taken from
“glace”
•Mr. Agassiz came to
Canada and concluded that Canada had been under an Ice Age, too
•Last glaciation from
2 m.y. ago to ~ 10,000 years ago
Reason for an Ice Age
•Don’t ask, no one
knows
•It prob. has to do
with the gases in the air
•If there is too much
CO2, the air gets warmed up (no chance of an Ice Age now, but can’t be 100%
sure)
•If there is too much
SO2, it reflects back heat, therefore, it is possible to get an Ice Age
•SO2 comes from
volcanoes, therefore, a big eruption can trigger an Ice Age
65,000,000 years ago
•An asteroid hit
Mexico in an area with lots of gypsum (calcium sulfate)
•The huge explosion
released tremendous amount of SO2 into the air that blocked sunlight for years
•The planet froze, plants
died, therefore animals who depended on plants died out too
•That is how the
dinosaurs & others disappeared for good
•Glacier = a river of
ice, needs a thickness of ~ 18 m before it can start moving
•Agassiz called it
“God’s Great Plough”, like a bulldozer
•Glacier can be in
mountains (alpine) or over continents (continental)
•Gives rise to
specific landscapes
•It is due to the landscapes
that Agassiz concluded that they formed from ice
Method of sculpting:
beware!
•Abrasion
•Glaciers are 2 – 3 km
thick, but it is not the bulk of the ice that breaks up hills & mountains
on land as it moves
•Water at the bottom
of the ice pile goes in small cracks in the rock below and expands into ice
•When water freezes it
expands ~ 10 % & breaks the surrounding rock
•So, the breaking up
of rock takes place silently UNDER the ice
Evidence for glaciation
in Canada
•Flatness of land
•Shallow lakes in
depressions, where bedrock was soft (water could not go away due to flatness)
•Smooth, polished rock
surfaces
•Glacial till (stones of
all sizes in the soil) left after ice melted
•Erratics (large
rounded boulders)
•Specific landforms
for alpine / continental glaciers
Erratics still in the
till
Direction of ice flow
in Canada
•Lakes lined up
indicates direction of flow
•Thickest pile of
snow/ice over Hudson Bay
•Bay depressed by the
load of ice (not deep)
•Bay rising today
slowly after load taken off (ice melted)
•From N to S in
Manitoba, local variations
•Ice moved from E to
W, north of the 60th parallel
Extent of the ice
Alpine landforms
•Glaciers flow
downhill into the sea
•U-shaped valleys with
tributary valleys
•Horn :
pyramid-shaped top of mountains
•Arete :
sharp-edged ridge between adjacent valleys
•Hanging valley with
waterfall
•Fjords : where
U-shaped valleys flooded by the sea, the most spectacular scenery
Horn
U-shaped valley
Alpine glaciers in valleys
Fjord
Preikestolen
Icebergs
Only place to see them floating in the ocean is Newfoundland (& Labrador)
They come into the sea at the southern tip of Greenland
They are pushed by the current up the Gulf of Baffin and down along east coast of Labrador & north coast of Nfld
They melt south of Nfld when they meet the Gulf Stream, a few km south of the Titanic disaster
Glacier falls …..
Arctic glacier collapses: too close for comfort
Continental glaciers
Esker : river below glacier
Kame / kame terrace : river above glacier
Moraine : glacial till where glacier stopped
The Manitoba “mountains”
The Pas Moraine
- Polished rock surfaces: roche moutonnee
- Drumlins : oblong hills of till, usually in groups
- Striations on polished rock surfaces
Striations
Eskers, kames terraces, Ice Flow in Manitoba
Esker
Kame Terrace, near Thompson
Drumlin
Permafrost country
Landscapes formed by repeated freezing / thawing of the ground
Soil “turning around” continuously, moving structures on the surface
Effect of permafrost
Soil flux (moving)
Palsa: organic material
Other permafrost landforms
Patterned ground
Pingo
Frost shattering, rock burst
KARST
Limestone / gypsum on the surface can be dissolved by water (water is a bit acidic)
Drainage moves underground (streams, rivers, lakes)
Limestone from Winnipeg to The Pas along the Interlake
a sinkhole
Cenote
Not a true sinkhole
Karst terrain, Guilin, China
Stone forest, China
Caves, Vietnam
Bahamas (means shallow water) Banks
Limestone with caves, sinkholes
The rise in the sea level sank those caves far below water
“blue holes”
LANDSLIDES
Mostly in the mountains
Everything on the slopes is unstable (gravity)
Slopes more the 33 degrees (angle of rest) slide
Only the roots of trees can keep soil in place
Grass, bushes not enough
Development of all kinds (houses, roads, etc starts with clear cutting, therefore vulnerable)
Half of landslide disasters in Canada
Are in the mountains
Worst disaster at Frank, Alberta, 1903 under Turtle Mt., locally known as “Rumbling” Mt. 77 died, museum along No.3 Hwy.
Coal mine underneath, torrential rain may have contributed
Surprise !
Quick clays in Quebec have ½ of landslide deaths in Canada
Clays formed in the ocean & salt component has dissolved leaving open spaces in the soil
Easy to trigger a landslide in such a soil
A heavy truck on the road, heavy rain, etc
Quick clays, Quebec
RIVERS
Mouths of rivers: end of a river
Most have a delta with sand deposits, like the Nile, Mississippi, Mackenzie (Deh Cho), Red river (Winnipeg beaches)
Some have an estuary, prob. because the tide won’t let the river drop its sand above water level. Examples are the Amazon, St. Lawrence (Kaniatarowanenneh = big waterway)
Watershed
A river with its tributaries & smaller streams makes up the Drainage Basin, or watershed
The river channel is V- shaped, can be deep
The river has a floodplain that it occupies during the spring or summer floods with natural terraces (levees) of sand/gravel/clay
The river deposits nutrients that plants need along its floodplain, that is why it is productive
Arctic watershed
Continental Divide
Separates watersheds that flow in opposite directions
For example there is C.D. that separates Manitoba rivers (flowing north) from the Mississippi river system (flowing south)
Sign says “ from here all rivers flow north”
On the other side: “ from here all rivers flow south”
Alluvium
The river brings gravel, sand along the bottom and lighter clay in suspension (what makes the water dirty-looking)
All these sediments are called alluvium
The amount of water in the river is its discharge (= depth X width X speed)
The mouth of the Amazon
Muddy but clean water
Meandering rivers (like Assiniboine)
When the topography is flat, the river zig zags across the floodplain
In a bend, its outer bank is undercut (gets deep) by faster water while its inner bank is slow with the river depositing sediment in a point bar – a place to look for gold, diamonds
Loops of the river can be cut off & form oxbow lakes ( like at Portage La Prairie)
Portage La Prairie
Red River
Most frequently flooded river in Canada
Problem probably because it flows north across various climates
Winnipeg protected by the Floodway that brings water around the city instead of going through the city
Portage Diversion takes the water from the Assiniboine into Lake Manitoba (which flooded last year), so it will not flood Winnipeg
The “Red Sea”, 1997
Drainage in Manitoba
Lowest elevation roughly stretches N-S in the middle of the province
Water from the Red river empties into Lake Winnipeg and flows north along Nelson River into Hudson Bay
Winnipeg river and Saskatchewan (Kisiskaciwani sipi = swift flowing) river flow into Lake Winnipeg
Nick Point
Rapids, an irregularity in the slope of a river
The water works to eliminate the nick point which retreats up-stream
Hydroelectric dams built on nickpoints where the falling water is used to turn a turbine lined with magnets, thereby creating electricity
Nick Point: Niagara Falls
First Hydroelectric Dam- in the world
Built at Niagara Falls
Statue of Tesla there: responsible for inventing every electrical device that we use
Big business ‘stole’ his invention
Nick point has moved 12 km upstream from the Niagara Escarpment (a rise in the land elevation) creating a deep canyon
Part of the St Lawrence Seaway
The “Great Lakes”: part of the St. Lawrence Seaway
Other rivers
Nile : longest
China’s longest: Yangtze
Widest : Indus (= son of God)
Thames, London, UK: only river with gates to prevent flooding (if the sea water moved up-river)
India, May 2016
51 degrees C
DESERTS: God of wind is in charge Aeolus
“Evaporation exceeds precipitation”
Hot or cold (Antarctic)
Sand covers only 20 % & is in constant move
Sand accumulates in dunes (steep slope is down-wind)
Erg is a sand sea
Many shapes of dunes, most common a barchan
Barchan dune: wind from the right
s :depression with spring water often below sea level
Animals / humans can suffer from dehydration
Slim chance of survival if unprepared
Taklimakan: “once you go in, you can never come out (alive)”
Kalahari: has a “skeleton coast”
Atacama: world’s driest place
Sahara: largest desert
New idea?
There is no rain in the desert, because there are no plants!
If enough plants are planted, evaporation could form clouds & rain
New plantations in the Sahara & Middle East –with water drawn from deep wells - may reduce size of desert
Soluble salts
Normally would be dissolved in water
Boron, salt, gypsum, sodium sulfate (detergent), sodium nitrate (explosives), potassium nitrate (toothpaste), lithium (batteries) lying about on the surface
Playas (dried up lakes)
More than 100 in N. America
Have encrusted salt (after water has evaporated)
Excellent racetracks, runways for planes, spacecraft (used by military, some are notorious for secrecy & biological experiments, such as Area 51)
Athabasca Sands
Northernmost dune field in the world
Sand blown from bottom of dried-up lake Athabasca during Ice Age
Buried some of the forest and keeps moving to the SE with the wind
Dead Sea
Along the Jordan river, no exit to the sea
Lowest place on the planet, 422 m below sea
Salty water makes it possible to float on water
35 % salt
World’s first health resort (visited by Cleopatra)
Lake Watrous, Sask. is similar
Sandblasting
Wind can move sand in the air
Erodes exposed rocks and shapes them aerodynamically - yardang
Wind can move sand in the air
Erodes exposed rocks and shapes them aerodynamically - yardang
Desert Pavement
Gravel on the surface
Don’t walk or drive over it!
The disturbance would release the sand from below
This would cause another sand storm!
Dust storm, China (explains Chinese eyes)
Dust storm over the Atlantic
Sydney, Australia
Loess
Worldwide deposits, but not in Canada
One of the best soils, spade marks visible for years, roof won’t cave in, rich in organic remains
80% silica, 10 % carbonates & phosphates
Yellowish -colors the “Yellow river” in China, also gives name to the “Yellow race”
Probably formed outwash of glaciers
Loess deposits in China
Uluru, Australia
The Olgas
Just before sunset
Dramatic change of colour
Wave cave
Method of sculpting
Forms at the bottom of the Uluru rock
Sandstorms are common with sand from the desert blasting a hole into the rock and shaping it like a wave
COASTAL
Erosion by waves
Movement of sediment by currents depositing off the shore and forming “barrier islands”
Longshore current: current along the shore
“Killer waves”: esp. in peninsulas (Oregon) Waves tend to eliminate peninsulas, so they converge on them with combined force
Sea level rise
- During last Ice Age was 120 m lower
Natives of Chile: “people arrived when sea was lower, then the sea rose and the peninsula (Chlh in ancient Greek) became an island” (today the island is known as Chiloe, also, the name of the country)
3,000 BC to 1,900 AD: no change
1900 – 1992: 1 – 3 mm / year rise
Since 1992: up more, variable, no agreement
Predictions
Predictions as good as yours: no one knows!
A 4 m rise will flood most of Florida
The Dutch (whose country is mostly below the sea) are prepared for a 7 m rise with massive fortifications
Australia gave orders to ~ 100,000 home owners to move away from coast – insurance /the country will not pay to relocate them!
The “sinking islands”
Paradises under threat, mostly atolls in the Pacific Ocean
Used to be volcanoes that became inactive
Erosion destroyed volcano, coral reefs formed around the island (due to warm, tropical conditions), then all that was left was a strip of land like an arc with shallow water in the middle (was the old, eroded volcano)
Shallow water inside with deep water outside the arc of land. Barely 1 – 2 m above sea level
Pacific Ocean
Polynesia (ancient Greek for “many islands”)
Melanesia ( “ “ “ “black islands”)
Micronesia ( “ “ “ “small islands”)
Pacific Island countries
Kiribati (1st to get new day, everyday)
Marshall Islands (includes Bikini )- USA related
Fiji
Tonga
Vanuatu (destroyed by typhoon, 2015)
Nauru (voted the happiest place on Earth!)
Tuvalu
Most have schools built by Canadian Government, volunteers urgently needed! (includes free fare)
Salty seawater: what is in it?
The results of weathering of rocks
98% of the “salts” have these 7 elements:
Sodium
Potassium
Calcium
Magnesium
Chlorine
Bromine
Sulfur
Tides: a powerful phenomenon
Only in big oceans (not in Hudson Bay, Mediterranean)
“pull” by moon, also the sun as they go around the planet (so, it is just gravity)
From 30 cm to 1.5 m
Highest at Bay of Fundy, Nova Scotia (up to 16 m high between low & high tide)
It is a RESONANCE affair!
Resonance
Push a child on a swing to learn about resonance
It is like the max. speed. Once you get it, one can push one-shelf further.
“Tendency to oscillate with a greater amplitude at a certain frequency than any other frequency”
Resonance depends on weight of person
So, basically how fast a body of water will swing, when the moon’s gravity acts on it
It depends on depth of water, how smooth the bottom is, etc
Tidal Day: 24 hours 50 min
Like a lunar day
If you keep watching the moon at the same time daily, it gets a little bit behind every day
Two high tides & two low tides per day
12 hours 25 min between two high tides
~ 6 hours between a high and a low
Bay of Fundy
“World’s largest bathtub”, funnel-shaped
Tides established here only 6,000 years ago
Water moves in & out of the Bay in sync with the tide the tide gets amplified
Average tide ~ 1 m
Silt, sediment & nutrients move in & out twice daily, therefore LOTS of MARINE LIFE : lobsters, crabs, clams birds, whales
Hopewell or Flowerpot Rocks
Cape Split
Narrow peninsula sticks towards the Bay
In front of it pass 14 b. tons water, equal to combined flow of all rivers /streams in the world
Hollow roar when turbulent water smashes on rock caves below (described by Ulysses?)
3 hours later the spectacle pauses & starts again flowing in opposite direction
St. John River, New Brunswick
The “Reversing Falls”: ‘confused waters’
due to tide moving up the river (if it is higher than the level of the river)
- a daily battle between the tide and the river
Tidal bore
Bore: Swedish/Norwegian word for “thunder”
A wave moving UP the river (due to tides)
Can be heard coming from far away with a loud noise (sound of an approaching train)
It is like a shock wave
Only observed in 60 rivers of the world with waves up to 10 m high
Good for surfing, rafting moves at 15-20 km/h
Pororoca, on the Amazon
Earth’s greatest (or longest) wave
Name means great destructive force
Can uproot trees from the riverbanks
Conditions: has to have large tidal range in the estuary & river bed has to slope gently towards the sea
The bore is the reason Amazon has NO delta
Tidal bore, China
Tombolo
Island close to the shore can slow down water currents and accumulate sediment
Eventually it forms a causeway linking island to shore
Gimli, Manitoba: used as a harbor
Barrier Islands, USA east coast
Other phenomena
A lesson from Peru
In the mountains, people lost their glaciers and they get very hot summers – don’t like neither do their animals
They painted their mountain WHITE
The glaciers are coming back
Won an International Award
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