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Posted By:
Hal Brown
Date Posted:
Sep 16, 2008
Description:
The Snake River takes a sharp turn at the Idaho border and opens into a broad valley for easy SeaRey flying. It wasn’t all easy, though. There was a strong temptation to deviate back into the mountains at Owyhee to visit the reservoir made famous by John and Carolyn’s adventures. Sometimes ferrying a SeaRey can be frustrating work.
The big open plain the Snake River flows through may have an outer space connection. Some geologists blame a great meteor impact for creating the plain.
From space, the Snake River plain looks like a world-sized bulldozer scraped a flat plain from southwestern Idaho northeast to a sharp point at the Yellowstone volcano. It is capped with lava flows, but unlike the Columbia Plateau it is not a massive outpouring. Instead it is underlain by rhyolite erupted from a long row of volcanoes that started about 13 million years ago.
The oldest volcanoes are in southwest Oregon and get progressively younger as they get to Yellowstone. Yellowstone is still an active volcano.
One theory to account for this strange line of volcanoes is a huge meteorite. About 17 million years ago it is postulated that a meteor struck Oregon with such violence that it ripped through the earth’s crust, exposing the upper mantle. The crater flooded with basalt magma to form a huge lake, spilling out into northern Oregon and Washington to form the northern part of the Columbia Plateau.
As molten rock poured out of the open wound, it relieved pressure below which perpetuated more outflow. Each volcano continued the process.
The process changed about 13 million years ago when continental crust was dragged over the open wound. Like a welding torch, the mantle magma cut a line in the crustal plate. The Snake River Plain is the track left by this process.
The Yellowstone volcano is about 300 miles to the northeast. This makes the rate of movement of the hotspot about an inch and a half per year. This fits pretty closely with the rate at which the North American Plate is moving away from the Mid-Atlantic Ridge.
It felt a little weird to be flying over what amounts to a long gash in the earth’s structure.
Date Taken:
Sep 16, 2008
Place Taken:
Near Weiser, ID
Owner:
Dan Nickens
File Name:
10_Into_Idaho.jpg - Photo HTML
Full size - <img src="/show.php?splash=SZTAK0000h">
Medium - <img src="/show.php?splash=SZTAK0000m">
Thumbnail - <img src="/show.php?splash=SZTAK0000s">
Category:
329, Taking Peli Home
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