seismic waves | earth geological and climatic history | cosmology & astronomy | khan academy Published 13 years ago • 244K plays • Length 8:38 Download video MP4 Download video MP3 Similar videos 5:58 pangaea | earth geological and climatic history | cosmology & astronomy | khan academy 9:22 refraction of seismic waves | cosmology & astronomy | khan academy 12:25 240 million years ago to 250 million years in the future 10:03 expanding earth and pangaea theory 1:02:58 slow earthquakes