1. Northwest Geology Unit 1: Defining the PNW
Note: Ms. Tharp is not a geologist, nor did she study Earth Science extensively.

2. Geological Vocabulary
Geology: history of the Earth and the natural processes that shape the planet.
Geologist: is someone who studies geology.
Evidence & the importance of rocks - Most geological knowledge comes from rocks. - Each rocks is unique, and contains a story. - Rocks are put into 3 categories according to the way they were made (igneous, sedimentary & metamorphic). - Geologists apply their knowledge of rocks to the natural landscape.

3. 3 Rock Types

4. Physical Landscape
Four major geological forces that have shaped the Pacific Northwest and created the most diverse physical region of the U.S.
Glacial Action
Flooding & Erosion
Plate Tectonics
Volcanic Activity

5. Geological Time
Most physical features of the PNW are considerably younger than the age of the earth.
Earth = 4.5 billion years
Oldest parts of PNW (eastern edges) = 1 billion years old
PNW comes into position = 570 million years ago
Realize: the PNW did not always exist as we know it today
Realize: the West Coast of most of North America was the Rocky Mountains
How? Small amounts of land were added to the PNW by erosion from rivers

7. Geological Eras…
Precambrian Eon: Pre-historic - the oldest era & Earth was covered by water. Paleozoic Era: million yrs. ago, continents were separated until “Pangaea”.

9. Geological Eras… Mesozoic Era,
millions yrs. ago. This is when the PNW began to take shape!! Pangea splits, plate tectonic movement creates the PNW we recognize today, sort of…

10. Geological Eras…
Mesozoic Era: Stage 1 Major mountain building, also a period of frequent volcanic activity. Cenozoic Era: Stage 2 63 million years – today Major mountain building, frequent volcanic activity, current landforms…when PNW REALLY began to take shape.

11. Last 1 Million Years
Climate Change – prior to Cenozoic Era, it was tropical here in the Northwest.
Cooling temperatures – rain became snow. Snow & ice accumulated over the landscape.
Massive Continental Glaciers were formed, thousands of feet thick.

12. Canyons & Coulees
Uneven spread of Continental Glaciers, called lobes (branches), that have tremendous force & erode the landscape.
Ice dams form and cause water to create a lake.
Water that seeps out of the lake creates canyons & coulees
Grand Coulee

13. Polson Lobe (branch) Located Northern ID & Western MT
Glacier Lake Missoula was formed.
Approx K yrs. ago Glacier Lake Missoula broke through the ice dam causing a massive flood.
Video: Sculpted by Floods The Northwest’s Ice Age

14. Global Warming Earth’s temperature warmed & glaciers melted.
Poured out into…
(1) The Pacific Ocean (2) Alpine & Glacier lakes, (Lake Washington & Sammamish) (3) Deep water bodies of seawater (Puget Sound & Strait of Juan de Fuca)
Partial flooding created “islands” (San Juan Islands, Vashon Island, Bainbridge Island) and shaped the Olympic Peninsula.
Leaving behind both glacier scares & very scenic landscapes.