Sediment core from a lake

False color CT scan of a core from Floras Lake, a coastal lake in southern Oregon that contains a record of tsunamis going back at least 6700 years. The beige (light) color is sand, which is more dense than the mud (brown, dark) surrounding it.

As the animation continues, the darker colors are hidden in order to highlight the lighter colors of the sand deposits. This helps scientists see amazing detail to help them form the sedimentologic "story" about how the sand was deposited.

The oval fragments of mud in the upper part of the sandy deposit appear to be rip-up clasts, indicative of an erosive, high flow into the lake that deposited beach and dune sand in the basin. This particular deposit is about 8 cm thick, and radiocarbon dating of sediments above and below the sand suggest that the tsunami was generated by a Cascadia megathrust earthquake roughly 2000 years ago.