1 Passage 1
How are the two passages similar?
Caves
by the National Park Service
A. They both present a person's reaction while in a cave.
B. They both show that some caves have lights added.
OC.
They both are fictional stories with characters and plot.
D. They both describe features of caves and how they form.
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Caves are naturally occuring underground cavities
large enough for human entry. Caves contain a large
number of minerals, of which calcite is one of the most
common minerals. Speleothems, often called cave
formations, are formed as rainwater passes
through the
soil and absorbs carbon dioxide. As water and carbon
dioxide mix, it forms a weak acid called carbonic acid,
which helps to dissolve underlying rock. When water
seeps into the air-filled cave it loses carbon dioxide to the
cave atmosphere causing the water to precipitate calcite
deposits in different forms. Calcite precipitates on ceilings,
walls, and floors as speleothems.
There are many types of speleothems, but the most
common that people are familiar with are stalactites and
stalagmites. Stalactites are formed by mineral rich
dripping water, and they grow down from the ceiling like
icicles. Stalagmites are formed when mineral rich water
drops from stalactites and accumulates on the cave floor,
growing upward like a cone. Sometimes a stalactite and
stalagmite grow together to form a column.