Time FACTS

PALEOZOIC ERA

• 579-230 millions of years ago (m. y. a.)
• Sedimentation of the Rocky Mountain area in west
• Early stages of mountain building process in the Rockies

MESOZOIC ERA

• Early building Blue Mountains

• Pacific Ocean extends to the western edge of Rockies

• Uplifting of the Cascade Mountains

• Retreat of the Pacific Ocean to west side of Cascade Mountain

CENOZOIC ERA

• Cascade, Blue and Rocky Mountains erode

• Sediment settles on Columbia Plateau

• Major volcanic flows results in construction of the Columbia Plateau

• Lava flows help create the Snake River Valley

• Uplifting of the younger mountains of the Cascade Range

• Wind -deposited soils made up of loess form the Palouse Hills

• Major Cascade volcanic peaks (Baker, Rainier, Adams, Hood, Shasta) very active

• ICE AGE

  Continental glaciers (5 or 6) periodically cover the northern portion of Washington, Idaho, and western Montana

  Columbia River's natural course blocked by the Okanogan Lobe

  Damming of river changes course causing glacial floods and formation of large coulees and Dry Falls

  18,000 y.a. Glacial floods (Lake Missoula) form the Channeled Scablands of WA

  15,000 y.a. Puget Lobe covers Puget Sound Trough to Olympia

  13,500 y.a. Most recent ice cap retreats, Pacific Ocean waters flood Puget Sound

• 10,000 - 14,000 y.a. Major volcanoes in Cascades frequently erupt (Native Americans moving into area)

• 6,800 y.a. Mt. Mazama's violent eruption, destroys itself; forms Crater Lake

• 5,700 y.a. Mt. Rainier's Osceola Mud Flow

• 450 - 1,500 y.a. Idaho's Craters of the Moon area was volcanically active

• 992 AD Major earthquake hits Seattle area in Puget Sound

• 1542 AD European explorers arrive in the Pacific Northwest

• 1914 and 1921 Lassen Peak, in northern California, erupts many times

• 1949 and 1965 Major Seattle earthquakes

• 1970s Mt. Baker and Mt. Rainier slowly simmer

• 1980 May 18 Mt. St Helens violent and deadly eruption

• PRESENT