Geo 1095: May 10, Day 860: Original Horizontality... Not!

Looking down the road from our pullout, you can see the slope of a few post-glacial lava flows, most notably the prominent one near the center of the photo. The post title refers to a principle of interpreting sedimentary rocks, in that the general assumption is made that sediments were deposited in horizontal or near-horizontal beds. If you want to get picky about it, that's not always precisely accurate, but it's a starting point, and it's accurate enough in the majority of cases. As we can see here, though, when we're dealing with lava flows, despite the superficial appearance of bedding, we can't start by assuming those "beds" were deposited horizontally. In this case, they were deposited on and parallel to the ground surface, which is pretty darned steep here.

A nice example of a basal breccia can be seen under the center flow.

Photo unmodified. October 9, 2014. FlashEarth location.