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Pits of Mystery
Transcript of Pits of Mystery
These formations can be seen at the Oregon Department of Geology and Mineral Industries' website at http://www.oregongeology.org/dogamilidarviewer/
The coordinates where some can be seen are Latitude 44.635594, Longitude -123.196366. How did they form? The leading theory is that during the Missoula Floods, icebergs were washed in the torrent to the Willamette Valley, where they got stuck on the floor of the flood plain. As the icebergs sat there, sediment washed up around them. When the flood receded and the icebergs melted, all that was left was a round depression in the soil. How they were found: These depressions were found by using Laser Imaging Detection and Ranging (LIDAR). Using this system, scientists can clear the landscape of all vegitation, revealing formations that are invisible using only aerial photography. What do these holes have to do with friction? Friction has more to do with these formations than most people realize. All four types of friction can be seen in the developent of these mysterious cavities. Types of friction Friction is the force that opposes motion. There are four types of friction. These are static, sliding, rolling, and fluid, in order of strongest to weakest. The End Rolling Friction As the iceberg is carried by the torrent, it touches the bottom, and rolls along the substrate. Static Friction As the water gets shallower, the iceberg stops moving altogether, due to static friction. Fluid Friction While the iceberg sits in the flow, the water rushes past, causing fluid friction. This causes the portion of the iceberg that is under water to become almost perfectly round. Static friction occurs between two surfaces that are not moving past each other. Sliding friction occurs between two surfaces that are sliding past each other. Rolling friction occurs between two surfaces when at least one surface is rolling past the other. Fluid friction occurs when an object is moving through a fluid, or when a fluid is moving past an object. Sliding Friction Particles of soil slide past each other in the flood, and as they encounter the iceberg, they are overcome by static friction, and settle around the rounded base. Summary Mysterious pits were found in the Willamette Valley due to LIDAR. These depressions can be explained as scars left by stranded icebergs, and can be more fully explained using all four types of friction. Bibliography "DOGAMI Lidar Viewer." Redirect - DOGAMI Home page. Oregon Department of Geology and Mineral Industries, n.d. Web. 5 Mar. 2013. <http://www.oregongeology.org/dogamilidarviewer
" Friction | CK-12 Foundation ." CK-12 Foundation - Student | CK-12 Foundation . Version 184.108.40.20657. FlexBook Platform, n.d. Web. 21 Feb. 2013. <http://www.ck12.org/book/CK-12-Physical-Science-For-Middle-School/r2/section/12.2/>.
"LIDAR/Pits of Mystery." Patton, Vince. Oregon Field Guide. Oregon Public Broadcasting. 14 Aug. 2011. Television. Questions How did they form?
Why are they round?
Why have they never been observed before?
When did they form?
What do they have to do with friction?