Tectonic Plates Earth's lithosphere is divided into tectonic plates that
float on the semi-fluid asthenosphere beneath. These plates move at
rates of a few centimeters per year, driven by mantle convection
currents. Interactions at plate boundaries can lead to earthquakes,
volcanic activity, and mountain formation. The theory of plate tectonics
explains the distribution of earthquakes and volcanoes. The movement of
plates also contributes to the recycling of Earth's crust.
Earthquakes and Volcanoes Earthquakes occur when stress along
geological faults is released, causing the ground to shake. Volcanoes
form when magma from the mantle reaches the surface, resulting in
eruptions. The Pacific Ring of Fire is a region with a high frequency of
both earthquakes and volcanoes. These geological events play a
significant role in shaping Earth's landscape. They also contribute to the
formation of fertile soils, benefiting agriculture.
Oceans and Seas Earth's oceans cover about 71% of the planet's surface
and contain 97% of its water. The Pacific Ocean is the largest and
deepest, followed by the Atlantic, Indian, Southern, and Arctic Oceans.
Oceans regulate Earth's climate by absorbing and distributing solar
energy. They are home to a vast array of marine life, from microscopic
plankton to the blue whale. Oceans also facilitate global trade and
transportation.
Freshwater Resources Freshwater constitutes only about 3% of Earth's
total water, with the majority locked in glaciers and ice caps. Rivers,
lakes, and groundwater provide the remaining accessible freshwater. The
Nile River is the longest, flowing through northeastern Africa. Lakes such
as the Caspian Sea and Lake Baikal are among the largest by surface area
and volume, respectively. Conservation of freshwater resources is vital
for sustaining life and human activities.
