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Liked pulled taffy: Pahoehoe lava |
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"Skylight" in a lava tube |
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Say A'a: Rough, sharp, and often colorful |
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1]
Cinder Cones are characterized by a central
volcanic vent with the accumulations of cinders (chunks
of lava riddled with gas holes), volcanic bombs and splatter
on the side of the cones. There are more than twenty-five
large cinder cones in the park, and we walked up to a couple
of them. There are four types of bombs in the park: spindle,
ribbon, breadcrust, and cow-pie. They are all formed in the
same way: globs of molten rock blast out of a vent or cinder
cone. Their ultimate shape depends on their flight paths,
how long they stayed in the air, and what they hit. Spindle
bombs are twisted, and cow-pie bombs look exactly like what
they're named after except some of them are over ten feet
long.
Lava tubes are the hollow tunnels that form
under the surface of lava flows and are shaped by the
withdrawal of molten lava. Some of these are huge -- we walked
through Indian Tunnel, which has a ceiling of forty feet and
is 800 feet long. There are natural skylights, making the
tunnel navigable without flashlights. Several other tubes
in the area require hard hats, flashlights, and caving experience.
The Caves Trail provides easy access to four of these lava
tubes.
During some of the eruptions, chunks of
volcano crater walls were carried like driftwood on the lava
flows and these wall chunks are known as rafted blocks. The
area around Devil's Orchard is full of these huge chunks of
rock that floated away from the craters.
One of the most fascinating things about Craters
of the Moon is seeing the different types of lava flows.
Pahoehoe is generally very fluid and looks like "pulled
taffy" in many places. It also forms stalactites of lava
and is often called "ropy" lava. A'a, on the other
hand, is very rough and sharp to the touch. The lava in the
Blue Dragon flow has tiny titanian magnetite crystals suspended
in the glassy surface and a range of colors, including bright
blue, can be seen. "Even though they look really different,
all forms of lava could come from the same volcano with the
'fresh, runny stuff' becoming pahoehoe and the 'older, crunchy'
lava being formed as a'a," according to geologist and
roadtripper Dan Sedenquist.
Since the most recent eruption was about 2,100
years ago, and the eruptions have occurred on a regular pattern
every 2,000 years, it seems like Craters of the Moon just
might be a very exciting road trip destination over the next
few years.
Mark
Sedenquist
September 4, 2005
