Transcript Document

The making of Washington: A Geologic History
Draw/color in the six cell table of your mini-poster
showing major events that formed WA State:
Create Mini-Poster That:
1. Visually shows 6 Major
Steps (by region, ex.
Eastern WA) that created
WA State – make colored
drawings.
2. Summarize what
happened in each major
event in right side column
(use headers)
3. Gives a time frame for
each major event (Add
dates).
File location:
Public/All/
Hagen Science 9/
Geo History of WA
Washington
doesn’t yet
exist!
Edge of
North
American
Continent
ends east
of Idaho
Direction
of plate
movement
200 million years ago:
Pangaea breaks up. North American
plate moves westward.
200
More than 50 separate terranes (large
blocks of mostly ocean crust) collide &
dock against the North American
continent.
Many of these terranes are “exotic”, having
travelled very long distances before colliding
with continent.
Continent
eventually
expands 400
miles westward.
A volcanic island arc moves toward the
continent
Volcanic arc pushes against Okanogan
sediments: Cascade Mountains formed
Erosion of the Okanogan terrane becomes
the eastern Washington plateau
Columbia
Plateau
Volcanic eruptions: Giant cracks form in
crust and spill lots of lava over the
Columbia Plateau
Columbia
Plateau
Basalt (lava) layers
pile up to form the
Columbia Plateau
Erosion of sediments from the Cascades
begins to fill the marine basin to the
west
The Olympic Mountains form by folding of
the continental crust and Pacific crust
Ice
Sheet
Snow melt from the Olympic and Cascade
mountains forms rivers.
The Cordilleran Ice sheet moves southward &
blocks the river exits into the Strait of Juan de
Fuca.
The Ice Sheet reaches its full extent
southward and begins to retreat.
The Puget Sound basin and Puget
lowlands are formed
Washington Today