My class of 7th graders are doing presentations in earth science.
We are focusing on How the Earth Changes. They would like for me to ask a
scientist how lava changes the earth? kdiener@nexus.chapman.edu
Kdiener
Hi Kdiener and 7th graders,
Lava changes the surface by very quickly emplacing a layer of very new and
hot rock onto the pre-existing terrain. Obviously, just about anything in
the way of the lava is either burned or buried, although depending on the
type of lava this can take quite a while. For example in Hawai'i we know
that 'a'a lava flows (the rough clinkery ones) travel quickly and can
easily push down walls, trees, and human structures. On the other hand,
pahoehoe, the smooth glassy type of lava moves very slowly and often will
pile up behind a flimsy wall of rocks that aren't even cemented together,
without pushing it over. Often the wall eventually gets buried but it
isn't pushed over.
This new rock may take many days to cool to the point that it is
comfortable to walk on. Depending on the amount of rainfall the rate at
which plants start to colinize the flow can be very different. There are
some flows on Kilauea that were erupted in 1987 that have many many young
trees and ferns on them. They are in a place that gets high rainfall and
it is just downwind from some pre-existing rain forest (a good source of
seeds). In contrast, there are some flows over on the west side of the
big island that are 100-200 years old and they look like they erupted
yesterday. On this part of the island there is almost no rainfall and
also no good source of seeds upwind.
Sincerely,
Scott Rowland
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