Interior of the Earth: Seismic Waves & others (1) Video Lecture | Geography for UPSC CSE

Seismic waves are vibrations that travel through the Earth's interior as a result of earthquakes or other geological activities. They provide valuable information about the Earth's structure and composition. By studying the behavior of seismic waves, scientists can determine the different layers within the Earth, including the crust, mantle, and core. The speed, direction, and amplitude of seismic waves allow researchers to infer properties such as density, temperature, and pressure within these layers.

The two main types of seismic waves are body waves and surface waves. Body waves include P-waves (primary waves) and S-waves (secondary waves). P-waves are the fastest seismic waves and can travel through solids, liquids, and gases. They cause particles to vibrate in the same direction as the wave's propagation. On the other hand, S-waves are slower and can only travel through solids. They cause particles to move perpendicular to the wave's direction. Surface waves, as the name suggests, travel along the Earth's surface and are slower than body waves. They are responsible for most of the damage caused by earthquakes. Surface waves include Love waves, which move side to side, and Rayleigh waves, which have both vertical and horizontal motion.

Seismic waves behave differently when they encounter a change in the properties of the Earth's interior. When seismic waves pass from one layer to another with different densities or compositions, they can be refracted, reflected, or absorbed. By studying the patterns of these interactions, scientists can identify the boundaries between the Earth's layers. For example, when seismic waves encounter the boundary between the Earth's crust and mantle, they experience a change in density and composition. This causes the waves to bend or refract, allowing scientists to determine the depth and characteristics of this boundary. Similar observations can be made at other layer boundaries, such as the mantle-core boundary.

Seismic waves themselves cannot be used to predict earthquakes with precision. However, they provide valuable information about the location and magnitude of an earthquake once it has occurred. Seismographs, instruments that record seismic waves, can be used to detect and measure ground motion during an earthquake. This data is crucial for emergency response teams to assess the impact and provide aid. Scientists continue to study seismic activity patterns and analyze historical data to improve earthquake forecasting and early warning systems. By monitoring seismic activity and detecting precursors, such as foreshocks or changes in ground behavior, they aim to develop more accurate earthquake prediction methods in the future.

Seismic waves play a crucial role in understanding the Earth's core. By analyzing the behavior of waves traveling through the Earth's interior, scientists have been able to deduce the existence and properties of the inner and outer core. For example, S-waves cannot travel through the liquid outer core, indicating that it is composed of molten iron and nickel. On the other hand, P-waves can pass through the outer core but are refracted or bent as they enter the inner core due to the increased density. This helps scientists determine the boundary between the outer and inner core. Additionally, the study of seismic waves has revealed that the inner core is solid, despite the extreme pressure and temperature conditions. This knowledge deepens our understanding of the Earth's internal dynamics and evolution.