Twenty-five million years ago, this area was a land of meandering streams and lush, rolling hills. Then came the first lave flow. Long cracks or vents opened in the earth and lava flooded the land spreading like water. The lava cooled and solidified into basalt. Lakes, swamps and streams reformed on the new, relatively flat surface. Then lava again flooded the land. The time between lava flows was sometimes only months; sometimes hundreds, even thousands of years. Each eruption reset the clock in a cycle that continued for 15 to 20 million years.
The layers of basalt visible in the valley walls are part of the largest lava fields in the world. It covers over 200,000 square miles in Washington, Oregon and Idaho and is reported to be over 10,000 feet thick in places.
This monument is dedicated to Professor George Beck, who for many years taught geology at Central Washington University in Ellensburg. Funds were provided by Yakima residents who have been interested in the teachings of Professor Beck.
This project was coordinated through the Washington Parks Foundation and erected with cooperation of the Department of Transportation and the Washington State Parks and Recreation Commission.
Toward the end of the lava flow cycle, the land began to rise forming the Cascade Mountains. Over millions of years of, tremendous pressure from beneath the earth's crust warped the flat basalt layers of this area into hills. In the geological structure directly ahead, known as the Umtanum Anticycle, the basalt layers were folded by the immense, slow pressure.
The Cascade Mountains have changed the climate of the Columbia Basin to a semiarid plain. The Cascades form a barrier to the moist winds from the ocean.
Older than the Hills
Before the uplift of the Cascade Mountains, the Yakima River was a peaceful, meandering stream. The land rose across the river's path, but so slowly that the rate of erosion by the river equaled the rate of uplift. Although slow by human standards, the erosion was swift by geological standards, as is evident by the steep, narrow gorge cut by the river. However, the river current wasn't rapid enough to erode a straighter channel, so it retains its early meanders.
The layers of basalt exposed by the downcutting river are part of the rock record of the lava floods that created the Columbia Basin.