Zone
2: Why are there ocean basins, continents, and mountains?
The convective motion of the Earth's solid mantle creates ocean basins, moves
continents across the face of the Earth (termed continental drift), and pushes
up mountains. Convection is the process of the buoyant rise of hot rock and
the sinking of cooler rock, and is the main way in which heat is lost from
the interior of the Earth. Interactive videos showing the convection currents
give visitors the chance to see and understand how the process works.
Upon
entering this zone, visitors walk beneath a suspended
model of a section of the Earth's lithosphere -- the crust and rigid
part of the upper mantle -- spanning the Gulf of Mexico, across North America,
and to the Northeastern Pacific Ocean. In addition, videos further explain
how plate tectonics -- the theory that the Earth's crust
is divided into a number of rigid plates that are in motion relative to each
other -- continually reshapes the planet's topography. Further along in this
zone, two sandstone rocks -- one from Siccar Point, Scotland and one from
Monticello, New York -- originally deposited at the same time near each other,
but then separated by the spreading of the Atlantic Ocean, through plate tectonics,
once again stand side-by-side after millions of years.
This
zone also contains a massive 3'6"-diameter bronze globe,
which visitors can actually rotate; the globe reveals the most accurate details
of the Earth's topography today. Based on military data sets, this globe offers
visitors a chance to actually feel the Earth's surface, from its deepest ocean
basins to its highest mountain summits.
To show how mountains
such as the Himalayas form, the plate tectonics zone features a
model created out of layers of sand. When two continental plates collide,
one plate is pushed beneath the other. Meanwhile, on the surface, land masses
are pushed up, and the Earth's crust thickens and folds into peaks and valleys.
The sand model provides a unique opportunity to visualize what would normally
take millions of years to occur -- uplifting, folding, crustal thickening,
and faulting -- all of which play vital roles in mountain building.
Also included in this
section are numerous specimens and casts from volcanic "hot spots" and prime
earthquake regions around the world. Lava samples from Hawaii; a sequence
of volcanic ash from Mount Vesuvius in Italy; and a boulder of obsidian from
the Medicine Lake Volcano of the Cascade Mountains in northern California
are all evidence of the forces at work beneath the Earth's crust. As powerful
as volcanoes are, their strength does not compare to the force of earthquakes,
which can be felt throughout the planet. A model of an outcrop showing the
ground rupture caused by the 1992 Landers earthquake in California reminds
visitors of these potent forces.
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