Fountains of liquid rock light up
the night. As the rock
is tossed up into the air it
begins to cool and
harden. It may plop
down as a soft lump or a
cinder-like piece of rock
filled with bubbles.
The bubbles are caused as
gases and water in the rock
expand. The gases have
been released from the
pressure of tons of rock
pressing down on them and
they expand and escape into
the atmosphere, leaving the
shapes of their broken
bubbles in the rocks.
As we learned
in States of Matter, physical substances
can exist as solids, liquids, and gases. Temperature affects
which state they will be in.
We are used
to seeing all three states with
water. We have seen ice, liquid
water, and steam. Still, it is hard to think of rock as being
liquid. Volcanic eruptions show us liquid rock, and, when the
lava cools, the rocks are often preserve patterns that look like
flowing streams or thicker
is some lava that has just begun to cool. Look at the rock surface
wrinkling as the soft molten lava spreads out. This rock is becoming
pahoi-hoi lava with its smooth wrinkled coils.
Notice how the
shell-shaped piece of lava at the upper right side of the picture
has cracked. Many substances expand when they are heated and
contract when they cool. As this rock cooled it contracted so
much that it cracked in several places.
When wind blows
dust and ash over the lava fields, some of the small particles
will blow into these cracks. Life will begin to take root in
cracks like these.
photograph from DHD
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