Washington State Chapter 1 Geologic History Geologic Processes Plate An idea used by geologists (people who tectonics study the natural processes & history of the Earth) to describe how land and landforms such as mountains, hills, plateaus, etc… are created and positioned throughout the world. Crust The outer layer of the Earth that we live on Mantle Directly beneath the crust; extremely hot & melt rocks to form molten magma (lava) Outer core Below the mantle; even hotter than the mantle; made up of melted iron & nickel Inner core Below the outer core/center of the Earth; composed of same material as the outer core but is the hottest layer of all. Geologic Processes • All layers under the crust are extremely hot • The rule: heat (whether it’s boiling or hot air) generally rises • Hot molten magma rises to the surface – when it reached the surface, it cracked, or fragmented, the crust into many pieces • Geologists call these pieces tectonic plates. Tectonic Plates • Like puzzle pieces; fit together to form a picture but not one solid piece • Made of solid rock • Sit on top of the mantle (made of molten magma) Tectonic Plates • Because of this tectonic plates are not in a constant position • They float around, moving slowly over millions of years, crashing into one another – movement is caused by the rising of molten magma • Movement of the plates causes the formation of major physical landforms (mountains, hills, plateaus, etc…) Tectonic Plates – 3 types • Divergent – move away from each other; usually occurs on floor of ocean; result of magma rising through the plates; magma hits the water & becomes solid rock called volcanic ridge • Transformant – two plates heading in opposite direction brush against each other; sliding motion; most of the time it’s a horizontal movement • Convergent – direct head on collision - 2 types of plates involved: Oceanic plates (in the ocean) Continental plates (ones that continents sit on) Tectonic Plates of the World Earth has 30 plates that drift on the mantle – throughout history the number of plates has changed. Plate Movement • Greatly affected Washington’s landscape • Waves of the Pacific Ocean used to crash against western side of Rocky Mtn’s • Juan de Fuca plate—helped to form the Cascade Mtn’s Mountain Building Process Results of tectonic activity is important to understand – especially living in WA state – as it is the reason behind all the mountains 1) UPLIFT – a heavier plate pushing up underneath a lighter plate, thereby pushing the land of the lighter plate up. Mountain Building Process 2) Volcanic Activity – one plate pushes up another (not only land but magma) the result is the creation of volcanoes volcanoes build mountains by erupting lava & ash Volcanic Eruptions • 2 types of eruptions: vertical lateral Volcanoes • Most visible natural force affecting WA • Most recent LARGE eruption occurred at Mount St. Helen’s in May 1980 (http://www.youtube.com/watch?v=rbgAOfv-W20) • Dormancy – term used to describe time between eruptions May 1980 July 2011 Dormant Volcanoes • In WA state: Mt. Rainier, Mt. Adams, & Mt. Baker • When these erupt, the Mt. St. Helen’s eruption will have been child’s play • Native American folklore tells stories of these now dormant volcanoes Ring of Fire • Name comes from numerous active faults and volcanoes that dominate the area Earthquakes • Happen when seismic waves travel through the surface of the Earth’s crust, causing the land to shake & vibrate • Energy released from a single point called the epicenter • Occur along active fault lines (faults occur when 2 different plates of crust touch) • Faults grind and move slowly against each other • When a fault gets stuck, pressure builds & when it’s released an earthquake happens Earthquakes • Charles Richter seismologist developed the machine that records ground movement during an earthquake – called a Richter Scale uses numbers 1-10 to measure 1 = weakest earthquake 10 = strongest earthquake for every increase of a whole number on the Richter scale, the intensity of the earthquake increases 10 times. • Thanks to Richter we can: gain knowledge on how ground moves & be better prepared for future earthquakes Largest earthquake in N. America – Anchorage, Alaska 1964 measuring 9.2 on the Richter scale Nisqually Earthquake on Feb. 28, 2001 measured a 6.8 on Richter scale Forces of Ice • Ice is another major factor that has formed WA state’s landscape • Continental glaciers (thick, massive ice sheets slowly moving across the landscape over long period of time) moved as far south as Olympia and the Columbia River • Glacier branched out into lobes (3 of them in WA state) Puget Lobe, Okanogan Lobe & Polson Lobe • Avalanches & alpine glaciers erode slopes of WA volcanoes and mountains Forces of Ice • Alpine Glaciers – located on the sides of mountains or in mountain ranges they break rock & carry it along its path down the mountains • 1/3 of all alpine glaciers in the U.S. are found in WA state (Mt. Rainier has 26 of them) Erosion • Natural agents such as water, ice, wind, and waves wear away landscapes, thus altering them. • It removes pieces of rock, sand, & soil from one place and depositing these same substances in another location. Ex: river cuts away at its bank, picks up rocks & soils which are deposited down river. • Through erosion, landscapes are destroyed, while others are built up. Landslides • The rapid collapse of debris, such as dirt, rocks, and boulders, from a higher elevation to a lower elevation. Changes in landscapes can be: damming streams into lakes widening valleys altering mountainsides • Washington’s numerous physical features are all visual reminders of the power of land, rock, ice, water, and wind.
Pages to are hidden for
"Washington State Chapter 1"Please download to view full document