Travel Reference
In-Depth Information
kettle pond.
A pond formed in a depression caused by the ground collapsing when a buried block of
glacial ice melted. Also called kettle hole.
lava.
Molten rock that has risen from below and flowed out on Earth's surface.
limestone.
A
sedimentary rock
composed mainly of
calcium carbonate.
magma.
Liquid or molten rock, including any dissolved gases and crystals, found deep within Earth.
meander.
The winding, snakelike turning course of a river that flows very slowly over nearly level ter-
rain.
mesa.
An isolated flat-topped mountain, usually more extensive than a
butte
but less extensive than a
plateau.
metamorphic rock.
A type of rock formed from preexisting rock by natural processes such as heat and
pressure, without melting the preexisting rock.
moraine.
A pile of rock debris carried and then left behind by a melting glacier.
mud pot.
A bowl-shaped area where steam rises in bubbles through rock that has been chemically
changed into clay.
obsidian.
A form of
rhyolite lava,
usually black, that cooled so quickly upon contact with air that crys-
tals did not have time to form.
paint pot.
A
mud pot
colored by
iron oxide
and other oxides.
perpetual spouter.
A
hot spring
that erupts continuously, as opposed to a
geyser,
whose eruptions oc-
cur between periods of quiet.
petrify, petrification.
A process whereby wood is turned to stone (fossilized) by the infiltration of water
containing
silica
or
calcium carbonate,
which replaces the woody material.
pH.
An indication of the acidity or alkalinity of a solution; a value of 7 represents neutrality. Lower num-
bers show greater acidity and higher numbers show greater alkalinity. The symbol comes from Ger-
man
Potenz
(“power”), and H, the symbol for hydrogen.
pitchstone.
An old name for
obsidian,
so-called because of its resemblance to hardened pitch.
plate tectonics.
The widely accepted theory that large slabs (tectonic plates) of Earth's outer layer move
about on top of the weaker layer below.
Precambrian.
The oldest geologic age for rocks on Earth, from the time Earth was formed some 4.6 bil-
lion years ago until 542 million years ago.
rhyolite.
A type of volcanic rock or
lava
that is relatively high in
silica
content; it is viscous (like asphalt
or molasses), so flows slowly.
sedimentary rock.
Rock formed from the weathered products of preexisting rocks that have been trans-
ported, deposited, and cemented.
serotinous cone.
A type of evergreen cone that opens and releases its seeds only in the intense heat of a
fire, ensuring that forests of pines such as lodgepole replace themselves quickly.
shale.
A very fine-grained, clay-rich
sedimentary rock
that breaks into thin sheets.
silica.
The chemical compound made of oxygen and silicon, the first and second most abundant ele-
ments in Earth's crust.
siliceous.
Adjectival form of
silica.
sill.
A layer of igneous material that squeezed between and parallel to the layering of preexisting rock
while it was molten, and then cooled below the surface. Compare with
dike.
