Download TECTONIC PLATE MOVEMENT Tectonic plates rest on the

TECTONIC PLATE MOVEMENT
Tectonic plates rest on the asthenosphere, a layer of soft, hot rock. Rock in this layer
and in the mantle just below it moves by convection currents. You have seen
convection currents if you have ever boiled a pot of water. The water at the bottom of
the pot heats up, becomes less dense, and rises. At the surface, it cools, becomes
denser, and sinks, only to be heated and rise again.
The rock in the asthenosphere
acts in a similar way. Magma
from the Earth’s core is superheated and rises towards the
crust. As it rises and travels
away from the hot core, it
begins to cool. The cooled
rock then sinks down again
towards the core where it is
heated. Then, the hot, soft
rock rises, cools, and sinks,
and is heated and rises again.
Convection currents in the mantle are much slower than those in boiling water. The rock
creeps only a few centimeters a year. The diagram shows convection currents
circulating. The tectonic plates in the lithosphere are carried on the asthenosphere like
long, heavy boxes moved on huge rollers. Over millions of years, convection currents
carry the plates thousands of kilometers.
As plates shift, one plate cannot move without affecting the other plates nearby. Plates
can move apart, push together, or scrape past each other. Plate movements cause
great changes to Earth’s crust. Most major geological events, including earthquakes,
volcanoes and mountain ranges occur where tectonic plates meet.
The map shows Earth’s major tectonic plates and the directions in which they move.
They are the African, the Antarctic, the Australian, the Indian, the Eurasian, the Nazca,
the North and South American, and the Pacific plates.