Those of us who live in south-central Eastern Washington live on the Plateau, which is made of over 300 indivdual eruptions of .

Those of us who live in south-central Eastern Washington live on the Columbia Plateau, which is made of over 300 individual eruptions of flood basalt.

Explanation:

Columbia plateau or the Columbia basalt plain that contains the area of about 100,000 square miles is formed due to the continuous flowing of basalt. It results due to the volcanic eruption of the lava that solidifies into basalt on the surface and it has taken about 10 to 15 million years period of continuous eruption or lava flow to form this columbian plateau. This region is spread across the Washington, Oregon and Idaho states of U.S.