Part 2: Willamette Valley Climate and Geology Its Geeky Science Sunday once again and I want to continue on with our look at the Willamette Valley. I am going to take you on a time trip; it will be kind of like Wells little novella, except there arent any Morlocks and we arent going forward in time. To do this, lets go back about 130,000,000 years. Prehistoric sea creatures are swimming in the Pacific Ocean along the Idaho coastline. Yes, Oregon is under the Pacific at this point. The North American tectonic plate has been on the move from its Eurasian and African plate siblings - and quite aggressively - in a westerly heading for hundreds of millions of years. The western edge of the plate has been in quite the battle with the ocean floor. The land has scar tissue of mountain ranges to prove it . The battles are about to become more heated. Mighty volcanic eruptions are commonplace and they are about to become even more common as the North American plate meets a network of fissures along the floor of the Pacific Ocean that spew incredible amounts of magma. Supposing that our time machine allowed us to still harvest information from 2013 and we could use a GPS indicator, you would see that we are currently positioned on the modern day border of Oregon and Idaho. I pull out the handy dandy telescoping telescope from my pocket and look out to the west. I hand you the telescope and say, Look right out there. You see that? That little volcanic island that you see is in the process of becoming what will be known as the Blue Mountains of Oregon. There are a whole network of these little islands out in the Pacific that are establishing the Oregon coastline. They are called the exotic terranes. In geologic terms, terranes are fragments of crustal material broken off from tectonic plates. These terranes are exotic because they actually came from another place. The volcanic islands moved along the sea floor until they reached the bigger and stronger North American plate. Some of these islands have begun welding themselves to the plate with large granite rocks known as batholiths and smaller rocks known as plutons. When the plate has a violent movement westward, it crushes the weaker lava rock that has not formed this granite bond and leaves behind large areas of crushed rock of various sizes called mélange. Let us jump into the time machine and head forward about 80,000,000 years. We are now standing in an age that was 50,000,000 years before the year 2013. Oregon now has a coastline that runs northeast along a bias from current day Grants Pass, in the southwest corner of Oregon, to Pendleton, Oregon, in the northeast corner. The coastline is rugged, with swampy inland areas that team with life. The last of the exotic terranes are now arriving following their Pacific passage and are forming what will eventually be known as the Oregon Coast Range; however, when in reference to this period, geologists have chosen to call it the Siletz Terrane. Much of the coast range is being formed underwater by lava tubes that cool and harden; this creates what is known as pillow basalt. Volcanic activity is also very prevalent farther inland from the current coast. A rim of volcanoes is quite active and every eruption layers the former seabed and inland swamps with tons of lava. This activity will mold and shape the Oregon Cascade Range over the next 44,000,000 years. Once again, we jump into our machine and travel to around 17,000,000 years ago. Weve returned to eastern Oregon and things are much different than they were when we were here 113,000,000 years prior. The volcanic activity has continued and has laid layer after layer of basalt for as far as the eye can see. Not to be overly dramatic, but this area hasnt seen anything yet. The most violent series of eruptions are about to begin with a fury that wont release its grip for another 9,000,000 years, with the most dramatic events happening in the first 2,000,000 years. These lava flows will be some of the largest and fastest that the world will ever see. Some rivers of magma will travel over 400 miles from their origins and the largest of these will cover 10,000 square miles. The equivalence of one-tenth of the state could be covered by one of these events and these series of eruptions will happen with unrelenting geologic frequency. Out of all of this violence will emerge one of Oregons most beautiful natural treasures: the Columbia River Gorge. Unlike say the Grand Canyon, which has been created through erosion, the Columbia River Gorge is built up layers of a type of basalt that cools in a very iconic column formation. These columns will, with layer upon layer of basalt from volcanic eruptions, eventually climb to 4,000 feet in some places right above a fissure in the crust of the earth that is slowly giving way under the strain of volcanic activity and the weight of lava. This is the creation of a geologic feature that will play a significant role in future events in Oregon. With this, we return to 2013. Upon our trip, we saw the establishment of the Oregon Coast Range, which makes up the Willamette Valleys western border. We have seen the beginnings of the Cascade Range that denotes the valleys eastern border and the origins of the valleys northern border - the Columbia River. Well continue the journey next week. Until then, Santé!
Posted on: Sat, 27 Sep 2014 06:50:12 +0000
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