Learn about Earth's layers, surface features, and rocks.
The Earth appears as a bright blue and round ball from space. It was formed about 4.6 billion years ago and is the only planet supporting life. The Earth's surface features include mountains, valleys, plains, and plateaus, all measured from the mean sea level.
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Earth's Surface Features
The Earth's surface is diverse, with high mountains like Mount Everest (8,850m) and deep ocean trenches like the Marina Trench (11,034m below sea level). These features are shaped by natural forces over time.
The Earth's interior remains largely a mystery due to high temperatures and inaccessibility. We learn about it indirectly through seismic waves, volcanoes, and other geological phenomena.
The Earth is made up of three main layers: the Crust, the Mantle, and the Core. The crust is the outermost layer, the mantle lies beneath it, and the core is at the center.
The crust is a thin, solid layer covering the Earth, varying in thickness from 60 to 100 km. It is thicker under continents and contains lighter rocks rich in silica and aluminium, known as SIAL.
Below the crust is the mantle, extending up to 2900 km deep. It is divided into the upper mantle (up to 100 km) and the lower mantle, made of silica and magnesium (SIMA). The mantle's movement causes geological activity.
The innermost layer is the core, about 3470 km thick, composed mainly of iron and nickel. It has an inner and outer part, with the temperature high enough to melt rocks, forming lava that shapes Earth's surface.
Rocks are naturally occurring solids made of minerals. They vary in hardness, shape, size, and color. Geologists classify rocks into three types based on their formation: Igneous, Sedimentary, and Metamorphic.
Igneous rocks form from cooled magma or lava, e.g., granite and basalt.
Sedimentary rocks form from sediments deposited over time, e.g., sandstone and limestone.
Metamorphic rocks are transformed by heat and pressure, e.g., gneiss and marble.
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Minerals and Rock Cycle
Minerals are inorganic substances found in rocks, such as iron, gold, and mica. The rock cycle describes how rocks change from one type to another through processes like weathering, erosion, and heat/pressure, forming a continuous cycle.
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