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Steamboat Rock viewing area

View on map:47.856913°N 119.103513°W

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Flood basalts on Steamboat Rock
47.856734°N 119.104439°W

Steamboat Rock
47.859686°N 119.098891°W

Steamboat Rock is a remnant left behind after the flooding.

Steamboat Rock is a section that was not eroded during the Missoula flooding - it is best viewed from this point.  The top of the area is littered with boulders (erratics).  Stop 6 in Baker et al. 

"Steamboat Rock (Fig. 26) is the remnant of a great cataract system that receded ~30 km from the coulee monocline all the way to the Columbia River. There must have been a temporary spill point at Steamboat Rock prior to the last recession ca. 17.2 cal ka, as indicated by the exhumation date for one of the inselbergs at Electric City noted above. The top of Steamboat Rock is littered with erratic boulders, and cosmogenic exposure dates for some of these are shown in Table 2 (see discussion below). The lava stratigraphy seen in cross section in Steamboat Rock and the walls of the Upper Grand Coulee are dominated by the N2 member of the Grande Ronde Basalt. They are capped by the Wanapum Basalt, commonly the Roza and/or Priest Rapids Members."

Description


Missoula Floods

The Missoula Floods (also known as the Spokane Floods or the Bretz Floods) refer to the cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age. The glacial flood events have been researched since the 1920s. These glacial lake outburst floods were the result of periodic sudden ruptures of the ice dam on the Clark Fork River that created Glacial Lake Missoula. After each ice dam rupture, the waters of the lake would rush down the Clark Fork and the Columbia River, flooding much of eastern Washington and the Willamette Valley in western Oregon. After the rupture, the ice would reform, creating Glacial Lake Missoula again.

References

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