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Stop 6: Lava Pit Crater

L ava Pit Crater was a walled lava lake. This formed by thick walls of basalt building upon themselves much like layers of candle wax holding melted parafin. Many small lava tubes are found around the top of the rim. Here again we see quantities of pahoehoe lava. As the lake level dropped the solidifying rock formed benches at each level around the perimeter. Time and gravity have pulled the benches into the crater floor. The crater was about 320 feet across at the top.

LEFT PHOTO: Looking across the top of the rim of the crater. Fellow students can be seen on the opposite ledge.

BELOW:Small lava tubes in the pahoehoe layers lace the top of the rim.

Stop 7: Tephra Cone and Red Bomb Crater

Only a few hundred feet away from the Lava Pit Crater is a crater of a much different nature. Here molten lava was ejected by jets of hot gas. Lobs of sticky lava were propelled up the throat of the vent. These bombs seem to have been kneaded into round "loaves" by striking the walls of the vent as they were blown out.

A small cinder cone was built in the center during the last of this volcano's activity. During eruptions of tephra a prevaling wind carried the ash and tephra to one side building up a much higher mound on one side.

Stop 8 and 9: Maar Explosion craters; East Twin and West Twin Craters.

Large resurgent craters were created by very violent explosions. Rising magma met a layer of ground water and flashed it to steam. The rapid expansion of steam exploded the overlying layers of basalt creating a crater. The proximity to the surface was sufficient to drop the pressure and temperature of the magma and it solidified without reaching the surface.

Stop 10: Dry Maar and Malheur Maar

Again we find a classical maar. Here like the Twin Maar Craters we just visited are two more craters that have been formed without the surfacing of any magma. Dry Maar is a little deeper than either of the East and West Maars. This maar is more sharply defined.

Directly north of the Dry Maar is the Malheur Maar. Surprise! It has a dark shimmering pool in the bottom and a dense ring of yellowed cattails. The water looks like it has no bottom, however, the guide suggests that this is an illusion due to the color of the water.

To Diamond Craters, Page 3


Created by STANLEY R. SANDERS, 1999