Last week was the bicentennial of Charles Darwin's birth. On today's date of Feb. 20, 1835, Darwin felt an earthquake in Valdivia, Chile, now estimated to have been of magnitude 8.5. The largest earthquake ever recorded by seismographs occurred in this same area, in 1960.
At the American Public Media web site, Speaking of Faith, you can hear an hour-long show on Darwin and his times (I haven't listened to it yet), and a short passage by David Kohn on the importance of Darwin's earthquake experience. It furthered his understanding of the possibility of gradual evolutionary change as part of a very long geologic history. This site also contains Darwin's earthquake "blog":
February 20, 1835
This day has been remarkable in the annals of for the most severe earthquake which the oldest inhabitants remember.— Some who were at Valparaiso during the dreadful one of 1822, say this was as powerful.— I can hardly credit this, & must think that in Earthquakes as in gales of wind, the last is always the worst. I was on shore & lying down in the wood to rest myself. It came on suddenly & lasted two minutes (but appeared much longer). The rocking was most sensible; the undulation appeared both to me & my servant to travel due East. There was no difficulty in standing upright; but the motion made me giddy.— I can compare it to skating on very thin ice or to the motion of a ship in a little cross ripple.