Where on Earth? - July 2011

Clues for July 2011:
1. This swirling mass of glassy rock is a hardened lava flow, formed during the final stage of a powerful rhyolitic eruptive sequence about 1,300 years ago. The volcano is a broad shield volcano that began erupting about 600,000 years ago, and has been active many times in the past 10,000 years.
2.  The first stage of the eruption that formed this feature consisted of tephra showers, which rained lumps of pumice and lava blocks that fell back into the caldera of the volcano. The tephra showers were followed by pyroclastic flows that swept down the slopes of the volcano to a nearby lake.
3. Finally, the lava erupted, oozing slowly down the inner wall of the caldera and ponding on the caldera floor. The volcano site is now a designated national monument.
Name the feature, the volcano and the state in which they are located.
Scroll down for the answer
 
 
 
 
Answer: The Big Obsidian Flow in Oregon’s Newberry Volcanic Caldera (Newberry National Volcanic Monument) is a solidified mass of volcanic glass that covers 2.8 square kilometers. Followed by tephra showers and pyroclastic flows, the obsidian flow oozed from the volcano during the final stage of a powerful rhyolitic eruptive sequence about 1,300 years ago. Photo is by Jim Ferguson.
July winners
Forrest Hopson (Reno, Nev.)
Robert M. Norris (Santa Barbara, Calif.)
Anne Sigleo (Newport, Ore.)
Tara A. Stolz (Niceville, Fla.)
Jeffrey T. Wilson (Northridge, Calif.)
 

To submit your photographs to our Where on Earth? contest, send them via e-mail to
earth@earthmagazine.org.

01 Jul 2011