Pre-U Geography CAIE

Tectonic processes and hazards

Tectonic Processes

• The Earth's crust is divided into large pieces called tectonic plates. These plates float on the semi-fluid layer of the mantle beneath.
• The movement of these tectonic plates is primarily powered by convection currents within the Earth's mantle, caused by heat from the planet's core.
• Where the tectonic plates meet are known as plate boundaries. There are three main types of plate boundaries: divergent, convergent and transform.
• Divergent boundaries are where two plates are moving away from each other, which allows magma to rise and create new crust. This often occurs under the sea, creating mid-ocean ridges.
• Convergent boundaries are where two plates are moving towards each other. If this involves two oceanic plates, one is usually forced under the other in a process known as subduction. This subduction can create deep sea trenches and trigger earthquakes.
• When a continental and an oceanic plate collide, the denser oceanic plate is subducted beneath the lighter continental plate. This process may lead to the formation of volcanoes and mountain ranges.
• Transform boundaries are where two plates are sliding past each other. This is associated with the creation of fault lines and can lead to strong earthquakes.

Tectonic Hazards

• Tectonic hazards include volcanoes, earthquakes and tsunamis. These are primarily caused by movements of tectonic plates.
• Volcanoes are typically found at divergent and convergent plate boundaries. They're formed when there's a buildup of pressure caused by rising magma.
• Volcanic eruptions can cause hazards such as lava flows, ash fall, pyroclastic flows, and volcanic gases that can have devastating impacts on human and natural environments.
• Earthquakes occur when stress accumulated along a fault line is abruptly released. This release of energy sends seismic waves through the Earth's crust, causing the shaking we feel.
• Earthquakes can cause a variety of hazards including ground shaking, surface rupture, landslides, and tsunamis. Major earthquakes can cause significant damage to buildings and other structures, and can lead to loss of life.
• Tsunamis are typically caused by undersea earthquakes at tectonic plate boundaries. The earthquake's epicentre displaces the sea bed, which subsequently displaces water, creating a series of waves that travel across the ocean.
• When these tsunami waves reach the shallow waters of coastal zones, they can increase in height and cause severe damage to coastal communities.

Remember: Understanding the processes behind tectonic hazards is key to managing and reducing their impact. By studying geography, we can help to mitigate the risks associated with these potentially devastating natural phenomena.