Chapter 3 – Interior of the Earth
- What is the interior of the Earth?
It refers to the structure beneath Earth’s surface, consisting of the crust, mantle, and core with varying temperatures and materials. - Why is it important to study Earth’s interior?
It helps us understand earthquakes, volcanoes, plate tectonics, mountain formation, and natural resources like minerals and geothermal energy. - What are the main layers of the Earth?
Crust (outermost), mantle (middle), and core (innermost). - What is the thickness of the crust?
Continental crust: 30–70 km; Oceanic crust: around 5–10 km. - What is the composition of the crust?
Mainly silicate rocks—continental crust is granitic; oceanic crust is basaltic. - What lies beneath the crust?
The mantle—extending up to 2,900 km below the surface, composed mainly of silicate minerals with iron and magnesium. - What is the core made of?
Primarily iron and nickel—also called “nife.” It has high density and extremely high temperature. - How do scientists know about Earth’s interior?
Indirect sources like seismic waves, gravity, magnetic field, and meteorite studies help reveal Earth’s internal structure. - What are seismic waves?
Shock waves produced during earthquakes. They travel through Earth and provide clues about its internal composition. - What are the types of seismic waves?
P-waves (primary), S-waves (secondary), and surface waves. - What are P-waves?
Primary waves are the fastest, longitudinal, and can travel through solids, liquids, and gases. - What are S-waves?
Secondary waves are slower, transverse, and travel only through solids—not through liquids. - What is the shadow zone?
An area where seismic waves are not recorded, indicating liquid outer core presence. - How do meteorites help in studying Earth’s interior?
They have similar composition to Earth’s interior, especially the core, offering indirect evidence of internal materials. - What is the Mohorovičić discontinuity?
Boundary between the crust and mantle—also called the “Moho.” - What is the Gutenberg discontinuity?
Boundary between the mantle and the outer core. - What is the Lehmann discontinuity?
The boundary between the outer and inner core. - What is the temperature inside the Earth?
It increases with depth—average geothermal gradient is about 1°C per 32 meters. - What is the pressure inside the Earth?
It increases with depth due to the weight of overlying rocks and materials. - What causes the Earth’s magnetic field?
Movement of molten iron in the outer core generates Earth’s magnetic field through the dynamo effect. - What is isostasy?
A state of gravitational balance between Earth’s lithosphere and asthenosphere, similar to floating icebergs. - What are the sources of Earth’s internal heat?
Radioactive decay, primordial heat (from Earth’s formation), and heat from core solidification. - How are earthquakes useful for geologists?
They provide seismic wave data that helps scientists map internal layers of the Earth. - What is the asthenosphere?
A partially molten layer below the lithosphere that allows tectonic plates to move over it. - What is the lithosphere?
The rigid outer part of Earth, consisting of the crust and upper mantle. - How thick is the mantle?
Approximately 2,900 kilometers thick—divided into upper and lower mantle. - What is the inner core like?
Solid due to extreme pressure, despite high temperature—composed mostly of iron and nickel. - What is the outer core like?
Liquid in nature, responsible for generating the Earth’s magnetic field. - What is gravity anomaly?
Difference between observed and expected gravity at a place—helps detect density variations inside Earth. - Why is the study of Earth’s interior challenging?
Direct access is limited; knowledge depends on indirect methods like seismic waves and laboratory simulations.