Earth's Interior

 

The Earth's interior is a lot more complicated than you might think. The interior of the Earth is filled with hot, solid rock that makes up about 80 percent of the planet's mass. The remaining 20 percent is a mixture of water, minerals and gases. The Earth's interior is divided into different layers―Crust, Mantle & Core. The crust is the outer layer of the Earth that surrounds its interior.  The mantle is the thickest layer of the Earth's interior.  The crust and upper mantle are made up of material that was once molten but cooled to form solid rock. The core is the third and innermost layer which comprises of inner core and outer core. 

Structure of earth:

The Crust:

➤Crust is the outermost or uppermost layer of the Earth's rigid outer shell, where our everyday lives unfold. A thin layer of solid rock that forms the solid exterior of our planet. 

➤The crust is made up of two main types of rocks: igneous and sedimentary. It is made up of large rocks such as granite, basaltic rock.

➤It is a relatively thin layer compared to the rest of the Earth's interior. It plays a crucial role in shaping our landscapes, hosting ecosystems, and providing resources.

➤The crust forms only 1% of the total earth's mass. The crust is divided into two parts―the upper crust(Continental crust) and the lower crust(Oceanic crust). 

➤The continental crust, which forms the continents, is less dense and composed of various rock types, including granite. On the other hand, the oceanic crust, found beneath the oceans, is primarily composed of dense basalt rocks.

➤The thickness of the continental crust is about 35 Km and composed of minerals such as Silica and Alumina, hence referred as SIAL. whereas, Oceanic crust is only 5 Km and composed of minerals such as Silica, Iron and Magnesium, collectively called as SIMA.

➤The SIAL has an average density of 2.7 and the SIMA has an average density of 3.0.

➤The crust and uppermost mantle combined together forms the earth's lithosphere. The lithosphere is not only responsible for the formation of Earth's diverse landscapes but also hosts ecosystems, provides habitats for various organisms, and influences climate patterns. The lithosphere is also a rich source of valuable resources such as minerals, fossil fuels, and groundwater, which are essential for human civilization.

Mantle:

➤The mantle is located just beneath the earth's crust. It composed mainly of silicate minerals rich in iron and magnesium, also called as SIMA.

➤The mantle consists 84% of the total earth's mass.

➤The thickness of the mantle is about 2900Km and has an density ranges from 3.4 to 5.5.

➤The upper mantle is known for its peridotite rocks, while the lower mantle undergoes immense pressure and temperature, transforming minerals into denser forms.

➤The uppermost layer/the asthenosphere is partially molten and exhibits a plastic-like behavior, allowing the tectonic plates to move. Below the asthenosphere lies the solid lithosphere, comprising the crust and uppermost mantle.

➤Deeper into the mantle, the transition zone called Mohorovicic discontinuity is occurred. It separates the mantle from the crust.

The Core:

➤The innermost layer is the core/barysphere―a dense and metallic region, further divided into the liquid outer core and the solid inner core.

➤It forms 15% of the total earth's mass.

➤The Earth's core is primarily composed of two elements: Iron (Fe)and Nickel(Ni) also called as NIFE.

➤The radius of the core is about 3900 Km. The average density of the core is 13.0.

➤The core experiences extreme conditions of heat and pressure. The immense pressure in the core prevents the iron and nickel from melting, despite the extreme temperatures.

➤The core is separated from the mantle by Weichart-Gutenburg discontinuity.

Rocks and Minerals:

Earth's history and the processes that have shaped it over millions of years. Our planet Earth is a treasure trove of fascinating rocks and minerals, each with its unique composition, properties, and significance.

Rocks, the solid foundation of our planet, have witnessed millions of years of geological transformations.

Rocks and their minerals are the building blocks of our planet.

Rocks are the solid materials that make up the Earth's crust, and they are composed of various minerals.

Rocks are the solid state material which can be hard or soft in nature. It also varies in size & texture and different in colour.

Minerals are the natural resources which occurred by certain physical properties and chemical composition. Iron, aluminium, gold, uranium, coal, petroleum and natural gas are some natural resources.

Rock cycle:

The rock cycle is a continuous process of rock formation, transformation, and recycling.

It involves three main types of rocks: igneous, sedimentary, and metamorphic.

The cycle begins with the formation of igneous rocks through the cooling and solidification of molten material. Over time, igneous rocks can be weathered and eroded, leading to the formation of sedimentary rocks. Through heat and pressure, sedimentary or igneous rocks can then undergo metamorphism, transforming into metamorphic rocks.

This cycle is a dynamic and ongoing process that has shaped the Earth's surface for billions of years.

Classification of rocks:

1. Igneous rock

2. Sedimentary rock

3. Metamorphic rock

Igneous rock:

Igneous rocks are formed from the cooling and solidification of molten material, either beneath the Earth's surface (intrusive) or on the surface (extrusive).

Igneous rocks are also called as primary rocks or parent rocks.

These rocks are generally harder, granular and no layers in it.

Fossils are not found in igneous rocks.

Igneous rocks originate from magma. They are associated with volcanic activities.

During the volcanic eruptions, the lava came through the vent and settles down.

The solidification of lava made solid hard material called igneous rocks.

when the lava cooled and solidifies beneath the earth's surface, it is called as Intrusive Igneous rocks. Also referred as Plutonic rocks. Examples of intrusive igneous rocks include granite, diorite, and gabbro.

when lava came out on the earth's surface and rapidly cools down which made the solid rock called Extrusive Igneous rocks. Also referred as Volcanic rocks. Common examples of extrusive igneous rocks are basalt, obsidian, andesite, and rhyolite.

The mineral composition of igneous rocks depends on the chemical composition of the original magma. Some common minerals found in igneous rocks include―Quartz, Feldspar, Mica, Olivine, Pyroxene.

Sedimentary rock:

Sedimentary rocks are formed by the accumulation and lithification of sediment particles. Sedimentary rocks are formed through a series of processes that involve the deposition, compaction, and cementation of sediments.

The sediments of various types of particles rolls down, accumulated and deposited over a longer period of time. The layers of the accumulated particles got unified and forms the solid material called sedimentary rocks. These type of rocks are soft in nature and get eroded easily.

Sometimes fossils got remained in the layers of the particles which preserves the remains of plants, dead animals and traces of ancient organisms. Fossils offer a glimpse into past life forms and contribute to our understanding of evolution and Earth's history.

Sedimentary rocks are economically significant as they host valuable resources like petroleum and natural gases, Coal and Groundwater etc,.

Ex: Limestone, Sandstone.

Classification of sedimentary rocks:

1. Organic sedimentary rocks

2. Mechanical sedimentary rocks

3. Chemical sedimentary rocks

Organic:

Formed by decomposition of plants and animals.

Contains fossils.

Ex: chalk, talc, dolomite, limestone.

Mechanical:

Formed by disintegration of igneous and metamorphic rocks.

Ex: sandstone, shale, clay.

Chemical:

Formed by precipitation of minerals from water.

Ex: limestone, dolostone, chert, gypsum.

Metamorphic rock:

Metamorphic rocks are formed when pre-existing rocks - igneous, sedimentary or other metamorphic rocks, undergo significant changes due to heat, pressure or chemical reactions. The process of metamorphism results in the recrystallization of minerals and the development of new textures and structures.

Metamorphic rocks are mostly crystalline in nature.

Metamorphism:

Thermal metamorphism(changes in rocks by high temperature ).

Dynamic metamorphism(changes in rocks by high pressure).

Some examples of metamorphic rocks are;

Basalt into slate

Granite into gneiss

Sandstone into quartz

Shale into slate

Limestone into marble.