Now take that and stand it up on its end. Thats the thickness of the ice mass which once crushed the Puget Sound area. Puget Sound wasn't even a sound then. Just a lowland between the Cascades, and a second set of mountains (The Coastal Range) further west. Mountains which now make up the Olympic Peninsula, Most of Vancouver Island, and the San Juan Islands.
Sometime around 18,000 to 12,000 years ago the Cordilleran Ice sheet plowed into this region from the north. It was 2km thick, massive, heavy! The ice found the path of least resistance and flowed primarily into the soft lowlands between the two mountain ranges. And there it sat. Heavily! it sat and it depressed the land! It didn't make the land want to write shitty poetry and slit its wrists (land has no wrists silly!), no it literally pushed it down! And it kept it down for thousands of years.
Warming trends began to melt the ice. As enough of it melted, waters from the Pacific Ocean were able to flow into the depressed lowlands and fill them in with sea water. Massive chunks of ice were still hanging around, and these form floating bergs that slowly melted in the water and dumped off the dirt, rocks, and other debris they had scooped and plowed up many thousands of years earlier onto the sea floor.
Over the years the depressed land began to spring back up. Much as the couch pillows slowly rise back up after my fat ass is done sitting on them. Landforms literally began to pop back up above the waters, and the sea receded. This didn't happen over night. As a matter of fact Puget Sound didn't take on its modern shores until about 5000 years ago or so. The rebound has slowed down as the land has popped back up (geologically speaking) to more or less its original elevation.
Some of the former mountains were flooded and now only their peaks show as the San Juan Islands, other islands became incorporated into the mainland as river deltas dumped silt over many thousands of years and eventually surrounded the former mountains with a mantle of rich lowland soils.
When whitey showed up in the 1850s and 1860s, they quickly found these former delta lands to be great farmland. Even today, as you drive along I-5, you see long stretches of flat land punctuated by occasional hills that just seem to stick up out of nowhere. These were once islands, but before that, they were mountain tops.
So there you go.
An ex-island near Burlington, Washington
when you put it like that (Sabin Hall to Vitucci's)... dude, that's nothing. I've walked that shit and on ice, no less. :D Thanks for the geology lesson!
ReplyDeleteI've done that trek myself a few times. But walking it is one thing. Imagine having to climb that distance to get to the top of the ice-sheet.
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