Interior Of The Earth (Advanced)

Interior Of The Earth

Sources Of Information About The Interior

Due to inaccessibility, the Earth's interior is studied using direct and indirect methods.

Direct Sources

Include rock samples from mining and drilling, as well as volcanic eruptions which bring up materials from deep layers.

Indirect Sources

Include analysis of seismic waves, gravitational force, magnetic field, and meteorites to infer internal composition and structure.

Earthquake

Earthquakes are sudden movements caused by the release of energy in the Earth's crust. The point inside the crust where it originates is called the focus, and the point on the surface is called the epicentre.

Why Does The Earth Shake?

Shaking is caused by stress accumulation and release along faults due to tectonic activity.

Earthquake Waves

Three types of waves: Primary (P) waves, Secondary (S) waves, and Surface (L) waves. P-waves travel fastest and through all media, S-waves only through solids.

Propagation Of Earthquake Waves

Speed and direction change with density and state of layers. Waves bend or reflect at boundaries, revealing internal structure.

Emergence Of Shadow Zone

Certain areas receive no seismic waves due to refraction or blockage (e.g., S-wave shadow zone confirms the liquid outer core).

Types Of Earthquakes

• Tectonic: Caused by plate movements.
• Volcanic: Due to volcanic activity.
• Collapse: Caused by collapse of underground mines.
• Explosion: Caused by nuclear or chemical explosions.

Measuring Earthquakes

Measured using seismographs. Magnitude: Richter Scale; Intensity: Mercalli Scale.

Effects Of Earthquake

Damage to life and property, landslides, tsunamis, fire, and changes in landform.

Frequency Of Earthquake Occurrences

Most earthquakes occur along plate boundaries. The Pacific Ring of Fire is the most seismically active region.

Structure Of The Earth

The Crust

The outermost solid layer, 5–70 km thick. Oceanic crust is thinner and denser than continental crust.

The Mantle

Extends to a depth of ~2,900 km. Upper part is partially molten (asthenosphere), allowing convection currents.

The Core

Composed mainly of nickel and iron. Divided into liquid outer core and solid inner core. Responsible for Earth's magnetic field.

Volcanoes And Volcanic Landforms

Volcanoes

Openings in the Earth's crust that allow molten material, ash, and gases to escape.

Shield Volcanoes

Broad and gently sloping, built by low-viscosity lava (e.g., Mauna Loa).

Composite Volcanoes

Steep-sided, formed from alternate layers of lava and ash (e.g., Mount Fuji).

Caldera

Large depression formed by collapse of a volcano after eruption.

Flood Basalt Provinces

Regions covered by extensive lava flows (e.g., Deccan Traps in India).

Mid-Ocean Ridge Volcanoes

Volcanoes formed along oceanic ridges due to sea-floor spreading.

Volcanic Landforms

Surface features shaped by volcanic activity including cones, domes, and lava plateaus.

Intrusive Forms

Formed when magma cools and solidifies below the surface, shaping underground rock structures.

Batholiths

Huge masses of intrusive igneous rock formed deep in the crust.

Lacoliths

Dome-shaped intrusions that push overlying layers upward.

Lapolith, Phacolith And Sills

Different shapes of intrusions based on orientation and space of solidification.

Dykes

Vertical intrusions that cut across rock layers and often serve as channels for magma.