The vast Montana landscape seems as though it's always been there, just like this, but we know better. It's a long story. The west side of the Rockies, which form one edge of the Flathead Valley, has quite a different tale to tell. https://flatheadlakers.org/explore/history-geology/ The short version is that when the massive continental glaciers melted ten thousand years ago, the bathtub-shaped valley filled with water held in place by an ice plug at the south end. When warm weather or the pressure of the rising water broke through, the water went out to eventually join the Snake and then Columbia Rivers on their rampage to the sea.
The East Slope of the Rockies is so different that it might be a different state -- probably ought to be. it's hard to understand that the volcanic pushing up and sideways of the tectonic plate under all the Pacific Ocean didn't just fuel the Pacific Northwest volcanoes and push up the Rockies, but also created a vast inland sea across the North American continent. That sea had much to do with what we see now: the buttes that were once reefs, the long slant of the altitude, the coal deposits, the clever coiled ammonite fossils that became what the Indigenous people called "iniskum," buffalo stones. Even the oil which was equivalent to a gold strike was created in those times.
https://en.wikipedia.org/wiki/Western_Interior_Seaway#Origin_and_geology
"The Seaway was created as the Farallon tectonic plate subducted under the North American Plate during the Cretaceous. As plate convergence proceeded, the younger and more buoyant lithosphere of the Farallon Plate subducted at a shallow angle, in what is known as a "flat slab". This shallowly subducting slab exerted traction on the base of the lithosphere, pulling it down and producing dynamic topography at the surface that caused the opening of the Western Interior Seaway. This depression and the high eustatic sea levels existing during the Cretaceous allowed waters from the Arctic Ocean in the north and the Gulf of Mexico in the south to meet and flood the central lowlands, forming a sea that transgressed (grew) and regressed (receded) over the course of the Cretaceous."
"The Bearpaw Formation, also called the Bearpaw Shale, is a geologic formation of Late Cretaceous (Campanian) age. It outcrops in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, and was named for the Bear Paw Mountains in Montana. It includes a wide range of marine fossils, as well as the remains of a few dinosaurs. It is known for its fossil ammonites, some of which are mined in Alberta to produce the organic gemstone ammolite."
https://en.wikipedia.org/wiki/Bearpaw_Formation
https://deeptimemaps.com/western-interior-seaway-thumbnails/
(Maps of the sea, which was really a succession of seas.)
Remarkably, all these phenomena and processes have names as though they existed now. They have real impacts on our lives. We can see what they left behind. But we have real impact on them as well. Only recently we've realized the impact when Europeans brought their diseases to America, the same diseases that had halved their own European populations in the past. When infectious invaders came from Africa and Asia through Europe to the Americas, they wiped out the human indigenous agriculturalist population so severely that the cessation of agriculture across the continents actually changed the weather by changing the proportion of plant-produced oxygen. Microscopic viruses and microbes changed the land masses from sea to sea, and restored the tropical jungles we are now cutting down and burning, changing the atmosphere once more.
This is echoed today when we look at the industrial revolution and the excess of greenhouse gases it has produced, warming the whole planet in only few hundred years.
"Anthropogenic climate change leads to melting glaciers and rising sea level. Between 1902 and 2009, melting glaciers contributed 11 cm to sea level rise. They were therefore the most important cause of sea level rise. Scientists have numerically modeled the changes of each of the world's 300,000 glaciers. Until 2100, glaciers could lead to an additional 22 cm of sea level rise."
https://www.sciencedaily.com/releases/2012/11/121114083819.htm
We're already imagining Manhattan submerged. Florida is already flooding.
No comments:
Post a Comment