Overarching controls Flashcards
What are the 4 overarching controls?
Geology, Glacial History, Physiography, Climate/Regime Control/Land use
System linkage- what is the importance?
- Hillslope coupling will have a direct impact on channel morphology and thus, biota
- knowledge of underlying material and its interactions with water which can help us understand system disturbances
What is the Western Cordillera geology?
-Landform in the west of Canada
-formed 200 mya
-ocean sediment and older rocks pushed east and
folded and faulted as they formed
-some rocks intruded by magma
-resulted in variability of mineral composition of rocks
What is hillslope coupling?
the interactions between a slope and a river
Coastal mountains
- interlocking igneous intrusions and metamorphic rock
- result of plate tectonics
- contains Canada highest peaks
Interior Plateau
- underlain by folded and faulted sedimentary and volcanic rock layers
- Fraser River Valley
Eastern mountains
- Sedimentary rocks that have been tilted, folded and faulted
- Columbia mountains and rocky mountains
How are physiographic regions classified?
- erosion
- deposition
- bedrock response to erosion
- orogenic history (event that leads to both structural deformation and compositional differentiation of the Earth’s lithosphere)
4 features of the B.C. Physiographic Region
1) 4 parallel mountain ranges
2) arranged by ascending order young –> old
3) Extending along N-S axis
4) Drained by several river (Fraser and Columbia)
How did glaciation impact the surficial geology of BC?
-created a thick sedimentary package overlaying bedrock
What is surficial material?
- deposits which lie on top of bedrock (not soil)
- deeper earth materials that lay beneath soil zone and bedrock
When did the Wisconsin glaciation occur? What was it?
approx 25,000 ya
ice sheet >2km that repeatedly advanced and receded
When did the rapid glacial melting to deglaciation occur?
What was the result of it?
Between 18000-11000 ya
Surficial geology of the lower Fraser lands
What is a U shape valley?
deep glacial trough through mountains formed from glaciers
What is drift?
any deposit of glacial origin
what is till?
unsorted/unstratified material left behind by glaciers (not water)
what is outwash?
sorted/stratified deposits made by glacial melt streams
What are some Glacial Surficial features?
Drumlins, Ground and end moraines, kame, kame terrace, outwash plain
What is a ground moraine?
blanket of till covering bedrock. Also called Lodgement till, a compact, dense, clay rich mound formed under the glacier.
what is an end/terminal moraine?
long, irregularly rounded, narrow ridge of till formed at the retreating edge of a glacier. Also called an Ablation till, made up of sand and silt, unstable and loose.
What is a Drumlin?
streamlined hill of till; tear dropped shaped with point in the direction of glacial retreat. more common in groups
Kame terrace?
a platform of till deposited who’s surface is higher than that of the valley floor.
outwash plain
- fairly flat, well drained plain
- formed by large quantities of meltwater
- commonly found infront of end morraines
kame
irregular shaped hill or mound formed in a depression on retreating glacier, deposited by melt water
-sand, gravel and till
Braided outwash plain
flat wide, unpredictable
- tons of sediment
- very unstable
Supra-glacial melt out till
made up of angular clasts with coarse unimodal grain size. Material eroded from the upper parts of valleys.
Sub-glacial melt out till
rounded, spherical clasts with bimodal distribution (silt/clay).
Ablation till
- Colluvial depoited onto glacier and then deposited into glacier, melt out of ice
- usually sand and silt
- ontop of lodgement till
- much looser than lodgement till
Lodgement till
deposited by a moving glacier; underneath glacier, compressed and compacted
-dense and clay rich
Glaciofluvial sediment
- materials transported by glacial river/melt water
- usually sands and gravels- more coarse, high flow
- worked beyond glaciers extent
(i. e GF outwash- well sorted, stratified and generally round clasts)
Glaciolacustrine sediment
formed in a lake where material was deposited by glacier meltwater(underneath glacier)
-v. fine material (silt and clay)
-settles perfectly level in a platy structure
-very erodible
-
till veneer vs. till blanket
veneer thin
blanket thick
What system classifies terrain?
BC terrain classification system
sgFGt-FI classify this terrain
Composed of sg-sand and gravel Parent material - Glaciofluvial Landform - terrace - means modified by Geomorphic process - slow down slope failure that are no longer active
