Download Shields, Stable Platforms, Young Mt. Belts

ANATOMY OF CONTINENTS:
Shields, Stable Platforms, Young Mt. Belts
Isostacy
Extra load cause depression of bottom
Mountain Building by Continental
Rifting
Wilson Cycle: First few
phases are visible in east
Africa and adjacent
regions.
Wilson Cycle: Doming and Fragmentation
East African Rift
Wilson Cycle: Continental Rifting
Rift Valley with Volcano - Tanzania
Wilson Cycle: Narrow Ocean Basin
Red Sea from space
Wilson Cycle: Wide Ocean Basin
Wilson Cycle: Destruction of Ocean Basin through
Subduction, beginning of the Orogeny
Japan: A volcanic arc formed as the Pacific Plate is
subducted
Accretion of the Island Arc – Now an Exotic Terrane
Accreted (Exotic)
Terranes of
Western North
America
Wilson Cycle: Final closing
of the Ocean Basin,
Culmination of the
Orogeny;
Continent – Continent
Collision
Himalayas from space. Mountains are snow
covered, India is to the left and Tibet to the right.
Isostatic Rebound: As
mountain erodes roots
rises.
•For every 1 km of mountain
eroded, only 2/3 of a km of
elevation is lost.
• Shield – deep interior of
mountain root exposed at
surface, high grade
metamorphic and intrusive
igneous rock.
•Stable Platform – sediments
from erosion of mountain are
deposited surrounding the
shield.
High Grade Metamorphic Rocks with
Igneous Instrusions
Orogenic events that created North America
Another round of the Wilson Cycle then splits
the old mountain belts apart
Pangaea 250 mya