What's under Mt. Hood? (2 of 2) (image) University of California - Davis Caption Rocks ejected from Mt. Hood show that the magma under the volcano has been liquid enough to erupt for less than 10 percent of the last 20,000 years. If generally true, this could have implications for understanding when a volcano is most ready to erupt. Credit Eric Klemetti, Denison University Usage Restrictions Maybe be used with acknowledgement of the source. 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.