Oregon Coast Field Trip Notes Rocks/Oceanic Crust/Geology

Topics: Oregon, Wind, Sediment Pages: 1 (407 words) Published: March 11, 2013
The Oregon Coast Range is composed of accreted oceanic sediments. The oldest rocks were formed during the Paleocene to the middle of the Eocene era. The rocks are gently folded and have a slight westward dip. As we walked out onto the Jetty, you could see how the waves came in at a slight angle rather than directly at the coast. Most of the rocks (particularly the smaller hand held size rocks) were jagged and triangular looking. This told me that these rocks came from a relatively close proximity. Also the pouring down rain and freezing cold told me that winter was here . The Oregon Dunes came from the coast range and is carried to the coast by the Umpqua River. Summer winds from N/NW and in the winter from S or SW and up to 100mph in storms. The Dunes are also on the move but the imported bushes/shrubbery (I can’t remember the name and I’ve looked!) hold the dunes in place by stabilizing the sand. Also we learned about saltation. Wind moves in one direction picking up fine particles of sand and blowing them in the direction of the wind and essentially moving the dunes after prolonged winds storms. Soil first starts to make its way to the coast by uplift from trees falling over, or steep hill sides. Once enough “loose” soil becomes heavy enough it begins to slide down a slope. As we saw on the field trip on the top of “unknown road” we could see the valleys in the mountain side where debri flows literally carved out trenches in the mountain and created an almost tunnel like path for the loose dirt to slide down. Once the dirt becomes loose and begins to slide it gathers with other dirt and picks up most everything in its past making it heavier and larger. Over time the accumulation of enough debri flows make paths down towards the Coast. The flows end up in rivers and settle on the bottom but with the current of the river it moves all of the soil and rocks it picked up and moves it towards the coast. If you imagine this spread across the Coast range,...
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