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

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 Rock Types

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

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

Geological Eras… Precambrian Eon: Pre-historic - the oldest era & Earth was covered by water. Paleozoic Era: 570-230 million yrs. ago, continents were separated until “Pangaea”.

Geological Eras… Mesozoic Era, 230-63 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…

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.

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.

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

Polson Lobe (branch) Located Northern ID & Western MT Glacier Lake Missoula was formed. Approx. 12-15K yrs. ago Glacier Lake Missoula broke through the ice dam causing a massive flood. Video: Sculpted by Floods The Northwest’s Ice Age

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.