Craters of the Moon National ParkSep 15, 2008
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Craters of the Moon National Park
Teri in Lava Cave
| Today, we visited Craters of the Moon National Park. This is a black somewhat desolate landscape. Craters of the Moon is special geologically because it is the largest and most complex of the late Pleistocene (the last Ice Age) and Holocene basaltic lava fields of the Eastern Snake River Plain. In the past 15,000 years eight major eruptive periods formed the Craters of the Moon Lava Field. During this time the field grew to cover 618 square miles. The Lava Field consists of up to 60 lava flows and 25 cones. It is the only place on the American continent where you can see the Great Rift. The Great Rift is a long line of fractures in the Earth’s crust. It begins at the base of the Pioneer Mountains and exists for over 50 miles to the southeast. This is where the astronauts trained before making the trip to the moon. We learned that three kinds of lava are found at Craters of the Moon. Block lava which is very dense and has a surface of angular blocks, aa lava which has a rough, jagged, or chunkier surface, and pahoehoe lava which has a smooth, ropy or billowy surface. We walked the lava beds on three different trails. The final trail was the one to Indian Tunnel (.9 mile each way). Indian Tunnel is a lava tube that has a 40 foot ceiling and is 800 feet long. Lava tubes are hollow spaces beneath the surface of solidified lava flows which are formed by the withdrawal of molten lava after the formation of the surface crusts. T was proud of her accomplishment, walking almost a mile then climbing down into the cave, out again, and back almost another mile. Not bad for a 60 year old, overweight smoker with arthritic knees. During the summer, as little as one inch of rain may fall in this area. This moisture drains quickly into the porous rock and out of reach of animals. Air temperatures soar into the 90's and the lava surface may reach 170 degrees F. Drying winds of 15-30 mph are common. It’s a desolate and somewhat forlorn landscape. We learned about the many creatures that eke out a living here and how they escape the summer heat in different ways. Most, like the mountain lion, venture forth in search of food only at night. Others, like the pika are active at dusk and dawn. Marmots take more extreme measures to escape heat. They enter a state of suspended animation called estivation, during which their metabolism and body temperature drop. They remain inert until cooler, moister conditions return. Since there are no streams and few water holes at Craters of the Moon, animals must get the moisture they need directly from their food. Mule deer munch bitterbrush leaves. Violet-green swallows snatch insects from the air. Rattlesnakes inject their venom and swallow squirrels whole. |
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