LAVA FLOW TRAIL
STOP 4
Squeeze-ups |
  As you walk along the trail you'll notice gaping fractures
in the rough basalt surface. Look between the rough walls of the fracture
and you'll see one of Bonito Lava Flow’s really cool squeeze-ups! Why
are they called 'squeeze-ups'? Follow along to find out... |
 Remember that Bonito Lava Flow was once just
that - a flowing river of glowing hot lava.
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 The top of the lava flow was exposed to cold
air, so it began to cool and solidify first. The core of the lava river
continued to flow while the top of the flow formed a rocky basalt roof.
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 Just like many other materials, rock shrinks
as it cools off. As the solid basalt cap began to shrink, gaping fractures
formed, pulling the sides apart. In some places, hot, semi-solid basalt
lava was able to squeeze up through the fracture. The semi-solid
lava is very plastic, like modeling clay or ®silly putty. As the lava
oozed up, it scraped the jagged, solid sides, creating grooves in the
plastic-like mass and, voilà, a squeeze-up was born!
Click
here to see another great squeeze-up. |
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