Columbia River Plateau

1086 Words5 Pages
Approximately 25 million years ago, all of Eastern Washington was flooded due to the eruption of the Columbia River Basalts. As the molten rock came to the surface, the Earth 's crust gradually sank into the space left by the rising lava. Explosions of magma filled the area and the coverage was extensive. The now Columbia River Plateau was filled with basalts and formed rivers through the areas of flow. Grande ronde and wanapum basalt was created by fissures about 17-15 million years ago and made up about 85% of the flow. Most of the Spokane Valley is covered by lava of the Miocene Epoch age. During the Pliocene and Pleistocene, great volumes of loess derived from the continental ice sheet. The land surface faced much erosion after the Missoula…show more content…
In the winter, the river flows at about 1,700 cfs due to the glacial runoff and in the summer the flow decreases as the temperature increases. Since meandering channels form on low slopes, the velocity is low and must flow through easily eroded bedrock which would be low sediments. The strongest current is on the cut bank where the larger rocks settle and in the point bar, where the slowest velocity occurs, is where deposition of small sediment falls. The river has low energy and therefore is a wide valley where the energy is directed side by side and eventually forms the meandering…show more content…
Also, there are cut banks where larger sediments are eroded due to the stronger currents. The Missoula flood was caused by deglaciation of glacial lake Missoula at the end of the previous ice age when the dams broke. It flooded Eastern Washington, specifically where the Spokane river is located. Glacial outburst flood deposits dumped much gravel and eroded basalt rocks into what we see today, such as the Bowl and the Pitcher. The flooding also brought up thick loess on either side of the river. The glacial floods created most of the familiar land forms that have come to define this river, the "dry" falls, mystifying basalt formations, giant ripple marks and unusual gravel bars. Also seen are shoreline and glacial features and processes in my vicinity.
The climate in Riverside State Park has an Average Annual Precipitation of 17.62 inches. The Average Maximum Temperature is 85.8°F in July, whereas the Lowest Average Minimum Temperature is 23.9°F in January. Also noted is the Average Annual Snowfall of 10.7 inches. Scientists are finding that the aquifer could be at risk with the climbing climate. It triggers an increase in rainfall rather than snowfall in the mountains resulting in less groundwater. Reduction of water supply is also because of streamflow timing due to increased

More about Columbia River Plateau

Open Document