KERITH CRATER
Iceland is an unusual center of volcanic activity in
the North Atlantic Ocean. It is the only place on Earth where a mid-ocean
ridge occurs above sea level. Iceland's volcanism turns out to be related
to both seafloor spreading and hotspot activity.
Below is a ~3000 year-old reddish scoriaceous basalt
from the Kerith Crater (Keriš Crater) (see
photo), a maar volcano in southwestern Iceland. Maar volcanoes
are subcircular depressions with a subdued, low profile, and are typically
filled with water. They form as a result of a steam explosion, the result
of groundwater being superheated by overlying hot lava flows.
Scoria
(8.0 cm across) from Iceland's Keriš Crater.
The reddish coloration is from oxidation. Fresh, unoxidized scorias are dark gray to
blackish-colored.