Key Points

The Earth is composed of three concentric layers: the crust is the solid outermost layer, the mantle is the thick semi-molten layer beneath it, and the core is the extremely hot, dense center. The crust and the upper part of the mantle form the lithosphere.

Proposed by W.J. Morgan, this theory explains that the Earth's lithosphere is broken into several large and small tectonic plates. These plates move slowly over the semi-molten layer beneath them, called the asthenosphere.

The movement of tectonic plates is caused by convection currents in the mantle. Heat from the Earth's core causes molten rock to rise and cooler rock to sink, creating a circular motion that pushes and pulls the plates.

There are three main types of plate boundaries: convergent (plates move together), divergent (plates move apart), and transform (plates slide past each other). These boundaries are sites of major geological activity.

When two continental plates collide at a convergent boundary, they can form massive fold mountains, such as the Himalayas. When an oceanic plate collides with a continental plate, it can cause volcanic activity and earthquakes.

The Ring of Fire is an area around the Pacific Ocean known for a high frequency of earthquakes and volcanic eruptions. This activity is caused by the movement and collision of tectonic plates along the Pacific Plate's boundaries.

Weathering is the process that breaks down rocks on the Earth's surface into smaller pieces without any movement of the material. The main types are physical, chemical, and biological weathering.

Erosion is the process by which soil, rock, and other materials are worn away and transported from one place to another. The main agents of erosion are water, wind, ice, and waves.

Rivers shape the land by creating V-shaped valleys and waterfalls in their upper course. In their middle and lower courses, they form meanders, oxbow lakes, floodplains, and deltas.

A delta is a fan-shaped landform created by the deposition of sediment at the mouth of a river. Deltas have highly fertile soil, making them ideal for agriculture, especially for crops like rice.

The constant action of sea waves erodes coastlines to create features like sea cliffs, sea caves, arches, and stacks. Waves also deposit sand to form beaches.

Glaciers carve the landscape, creating U-shaped valleys, cirques, and fjords through erosion. When they melt, they deposit debris called till, forming landforms known as moraines.

In arid regions, wind erosion carves rocks into shapes like yardangs. Wind also deposits sand to form various types of dunes, such as crescent-shaped barchan dunes.

In areas with soluble rocks like limestone, underground water dissolves the rock to create unique Karst landscapes. Common features include caves, sinkholes, stalactites, and stalagmites.

Landslides are the movement of rock, debris, or earth down a sloped section of land. They are caused by factors that make the slope unstable, such as heavy rainfall, earthquakes, and human activities like deforestation.

A GLOF is a sudden release of a large amount of water from a glacial lake. These are often caused by the failure of a natural dam due to glacier melting, avalanches, or earthquakes.