Palouse Falls (IMAGE) Washington State University Caption The Palouse River in southeastern Washington State drops nearly 200 feet through cliffs of basalt created by scores of lava flows 10 to 16 million years ago. Washington State University researchers have determined that one flow constituted one of the Earth’s largest known volcanic eruptions, a millennia-long spewing of sulfuric gas that blocked out the sun and cooled the planet. Credit Dean Hare, WSU Photo Services Usage Restrictions Please credit Dean Hare, WSU Photo Services License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.