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from the gonna-need-a-bigger-Band-Aid® dept.
When Doug Wiens approached Minnesota farmers to ask permission to install a seismometer on their land, he often got a puzzled look. "You could tell they were thinking 'Why are you putting a seismometer here?,' " said Wiens, professor of earth and planetary sciences in Arts & Sciences at Washington University in St. Louis. "'We don't have earthquakes and we don't have volcanoes. Do you know something we don't?' "
Actually, he did. Deep beneath the fertile flat farmland, there is a huge scar in the Earth called the Midcontinent Rift. This ancient and hidden feature bears silent witness to a time when the core of what would become North America nearly ripped apart. If the U-shaped rip had gone to completion, the land between its arms—including at least half of what is now called the Midwest—would have pulled away from North America, leaving a great ocean behind.
Weisen Shen, a postdoctoral research associate with Wiens, will be presenting seismic images of the rift at the annual meeting of the Geological Society of America (GSA) Sept. 25-28. The images were made by analyzing data from Earthscope, a National Science Foundation (NSF) program that deployed thousands of seismic instruments across America in the past 10 years.
At last, the real reason Lex Luthor was in Smallville, to split open the fault and create beach-front property in the Midwest.
(Score: 1) by khallow on Wednesday September 28 2016, @07:43AM
"We know that lava comes out at rifts," Wysession said. "The East African rift zone, for example, includes a number of active and dormant volcanoes, such as Mount Kilimanjaro. But the Midcontinent Rift was flooded with lava, and as it sank under the weight of the cooling basaltic rock, even more lava flowed into the depression.
"A huge volume of lava erupted here," Wysession said. "It was perhaps the largest outflowing of lava in our planet's history. And then, after the eruptions ended, the area was compressed by mountain building event to its east, thickening the scar by squeezing it horizontally.
I notice that they don't really know what was lava (something that reaches the surface) and what is magma. I guess someone needs to drill deep into those layers to see what's actually down there.
(Score: 0) by Anonymous Coward on Wednesday September 28 2016, @01:55PM
It was a spreading ridge - similar to the one in the middle of the Atlantic. When the plate was splitting apart, lava filled the gap. (It was on the surface, therefore it must have been lava at that point.) The lava cooled, dense rock sank, more lava filled in above the new - sinking - surface.
This was roughly 3 billion years ago; the surface has changed dramatically since then. (No current pools of lava sitting around disturbing the natives in their daily routines.) So it was lava at the time, is now basaltic rock that's mostly covered by topsoil.
I always figured a good way to earn an honorary doctorate would be to restart the rifting process and finally separate Minnesota and Wisconsin. Haven't quite worked out the details though...
(Score: 1) by khallow on Wednesday September 28 2016, @02:25PM
It was on the surface, therefore it must have been lava at that point.
Unless, of course, it wasn't on the surface. My point.
(Score: 2) by bob_super on Wednesday September 28 2016, @06:24PM
> "It was perhaps the largest outflowing of lava in our planet's history."
Of course. It had to be. Because USA.
Let's not talk about the events surrounding the formation of the whole crust of the planet, that would distract from the fact that, trust me folks, we have the biggest one right here in the US, and that makes it great.
(Score: 1) by khallow on Wednesday September 28 2016, @10:34PM