Summary
Chapter-2
The earth, our homeland, is a dynamic and ever-changing planet. From its surface to its core, various processes shape its landscape and composition. Have you ever pondered what lies beneath the surface? What materials make up the earth’s layers?
Interior of the Earth
Just like an onion, the earth consists of several concentric layers. The uppermost layer, known as the crust, is the thinnest of all layers, ranging from about 5 kilometers thick under the ocean floors to approximately 35 kilometers thick beneath continental masses. The continental crust is primarily composed of silica and alumina, referred to as sial, while the oceanic crust contains silica and magnesium, known as sima.
Beneath the crust lies the mantle, extending to a depth of approximately 2,900 kilometers below the crust. The mantle plays a crucial role in the earth’s dynamics and heat transfer.
At the earth’s core lies the innermost layer, with a radius of around 3,500 kilometers. This core is predominantly made up of nickel and iron, termed nife, and sustains extremely high temperatures and pressures.
Did You Know?
- The deepest mine in the world, located in South Africa, reaches approximately 4 kilometers deep.
- To reach the earth’s center, one would need to dig a hole approximately 6,000 kilometers deep on the ocean floor.
- The crust constitutes only 1 percent of the earth’s volume, while the mantle comprises 84 percent, and the core makes up 15 percent.
- The radius of the earth measures 6,371 kilometers.
Rocks and Minerals
The earth’s crust is composed of various types of rocks, natural masses of mineral matter. Rocks vary in color, size, and texture and can be categorized into three major types: igneous rocks, sedimentary rocks, and metamorphic rocks.
Igneous rocks form when molten magma cools and solidifies. Extrusive igneous rocks, such as basalt, are formed when magma reaches the earth’s surface and cools rapidly. In contrast, intrusive igneous rocks, like granite, form when magma cools slowly beneath the earth’s surface.
Sedimentary rocks are formed from the accumulation and compression of sediments, such as sand and silt, over time. These rocks often contain fossils of ancient plants and animals.
Metamorphic rocks are formed when existing rocks undergo heat and pressure deep within the earth’s crust. Examples include slate, formed from clay, and marble, derived from limestone.
The Rock Cycle
Rocks undergo a continuous cycle of transformation known as the rock cycle. Igneous rocks can weather and erode to form sediments, which then accumulate to create sedimentary rocks. Heat and pressure can alter these rocks to form metamorphic rocks, which can further melt and solidify into igneous rocks, completing the cycle.
Minerals and Their Significance
Minerals, naturally occurring substances with distinct physical properties and chemical compositions, are integral to various aspects of human life. Some minerals, like coal, natural gas, and petroleum, serve as fuels, while others, such as iron, aluminum, and gold, are essential for industrial processes. Additionally, minerals find applications in medicine, agriculture, and other fields.
Word Origins
- Igneous: Derived from the Latin word “Ignis,” meaning fire.
- Sedimentary: Derived from the Latin word “sedimentum,” meaning settle down.
- Metamorphic: Derived from the Greek word “metamorphose,” meaning change of form.
Glossary
- Fossils: Remains of plants and animals trapped in rock layers.
By unraveling the mysteries of the earth’s interior and understanding its composition, we gain insights into the forces that shape our planet’s past, present, and future.