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Dry Falls

Dry Falls, in eastern Washington State in the U.S.A., is a place of amazing geography. Millions of years ago, the area was over a hot spot in the earth's core. Magma repeatedly welled up, cracking through the surface, and spreading across the land as many as 300 times, separated by thousands of years. As each one cooled and hardened, it shrank and cracked, leaving many layers of five and six sided vertical columns of basalt, similar to the Giant's Causeway in Northern Ireland. The North American continent drifted to the northwest, and the now less active hot spot now provides Yellowstone National Park with its geysers.

Then about 20 thousand years ago, a massive ice sheet pushed south from Canada. Glaciers would block the Clark River in northwest Montana, creating a massive lake. The lake repeatedly broke through the glaciers, unleashing catastrophic floods across eastern Washington. The Columbia River valley overflowed and the water spilled south across the plains. Basalt columns were ripped away, leaving the vertical sided box shaped canyons called coulees. The waterfall at Dry Falls, flowing down the Grand Coulee, was 5 times wider than Niagara Falls, and estimated to be 10 times the flow of all current rivers in the world combined. Massive temporary lakes formed at bottlenecks. One such bottleneck was where the Columbia River penetrates the coastal mountains near the Pacific Ocean, and the water backed up Oregon's Willamette River valley to the south. Present day Portland, Oregon was under hundreds of feet of water, and melting icebergs from the glaciers dropped boulders from Canada as far south as Eugene, Oregon.

Today, the Columbia River is dammed near Grand Coulee, forming Roosevelt Lake. Water is further pumped up into Grand Coulee forming Banks Lake with earthen dams at the north and south ends. The southern end of Banks Lake is at the top of this map. I've rerouted the irrigation ditch from the east end of the south dam to provide water flow through the start square. Highways follow actual routes, though I've enlarged the east-west highway, adding interchanges, as well as a rail through the start square.

You may wish to stay away from that abandoned factory. It had been processing radium from uranium ore, and it now glows from radioactivity at night.

Thank you BonBonB for your kind remarks: https://youtu.be/61Vhgv_c8gw


Check out my other maps:

Orcas Island, at https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1858963662

San Mateo, at https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1967427825

Canyonlands: https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2170606329

Sebascodegan Island: https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2246391897