Here’s another YouTube video that explains the origins of pillow basalts. What’s really interesting, and something I hadn’t even considered, is that columnar basalt does form on the ocean floor as well. I’m consistently impressed with these deep sea images because they beautifully illustrate the formation of the top layers of the ocean crust.
Click here to see an earlier post with a video showing the actual formation of pillow basalts.
A friend of mine posted this video to my Facebook page and I thought it was awesome enough to warrant sharing on the blog. What I find really fascinating about this video is that you get to see how the basalts get that pillow like shape. As the basaltic lava flow comes in contact with the water, it quickly quenches into that bulbous shape. The lava continues to build-up in the pillow, and like blowing too much air into a bubble, basically bursts open and the process repeats itself.
What’s even cooler is that, through a process called obduction, those pillow basalts get heaved up onto the continent. Think of it as the opposite of subduction; instead of the pillows getting swallowed by the oceanic crust as it dives under the continental crust, it gets uplifted onto the land. In what is surely a perverse joke by nature, some of these pillow basalts can be found in Oregon. It’s as if nature decided we didn’t have enough basalt from the Columbia River basalt group, so it gave us sea-floor basalt as well.