Earth’s Structure, Rocks, Minerals, and Soil Formation
The Earth: A Unique Planet
Key characteristics of the Earth include:
- Presence of oxygen
- Temperature ideal for human life
- Abundance of water
Geosphere: Earth’s Internal Structure
Crust
The crust is the outermost layer of the Earth, where life unfolds. It represents only 2% of our planet’s volume. Its thickness is about 30km, and its temperature ranges from 22°C to 400°C.
Mantle
The mantle is the most voluminous layer, making up 82% of the Earth’s volume. It has a thickness of about 2870 km and is divided into:
- Upper Mantle: Consists of solid materials.
- Lower Mantle: Temperatures are so high that materials melt into a pasty mass called magma.
The temperature in the mantle varies from 1500°C in the upper mantle to 3000°C in the lower mantle.
Core
The core is the Earth’s innermost layer, occupying 16% of the total volume. It has a thickness of about 3470 km and is composed of metallic materials. Temperatures range from 4000°C in the outer core to 6000°C in the inner core.
Rocks and Minerals
Rocks
Rocks are naturally occurring solid bodies formed by one or more combined minerals. They can also be formed by mineraloids.
- Granitic Rocks: Share characteristics with granite.
- Basaltic Rocks: Predominant in the sea and are dark in color.
Minerals
Minerals are naturally produced solid substances. They are created through chemical processes that take millions of years to complete. Inside, particles are arranged in a regular order, forming solids called crystals. Each mineral has a particular type of crystal. For example, halite is common cooking salt.
Mineraloids
Mineraloids are natural substances found in the Earth’s crust that form over millions of years but do not have crystals in their structure, such as volcanic glass.
Classification of Rocks in the Earth’s Crust
The rocks composing the crust are of three types:
- Igneous Rocks: Formed by the cooling and solidification of magma.
- Sedimentary Rocks: Result from the accumulation and compaction of rock fragments transported by rivers, glaciers, oceans, lakes, and wind.
- Metamorphic Rocks: Igneous or sedimentary rocks that have been subjected to high pressure and temperatures within the crust, changing their original features.
Soils
Soil Formation
Soil is formed by the very slow weathering of rocks. Air and water enter the spaces between rock pieces, creating an environment for different types of life. Living organisms contribute waste that decomposes through the action of bacteria and fungi. Substances produced by decomposition combine with minerals, forming new dark minerals called humus.
Soils formed in the same place where weathering occurs are called indigenous soils. Chips and particles resulting from weathering that are carried by water or wind to other areas where they accumulate and form soil are termed allochthonous.
Components of Soil
The components of soil include:
- Water and mineral salts in solution, along with suspended clay particles
- Clay particles
- Fine sand
- Gravel
- Humus