Global Patterns of Earthquakes, Volcanoes, and Mass Movements
Understanding the global distribution of these hazards is essential for predicting risks and implementing effective management strategies.
Earthquakes: Shaking the Ground
Definition
Earthquake
Earthquake is a sudden releases of energy in the Earth’s crust, causing ground shaking.
They are primarily concentrated along tectonic plate boundaries, where plates interact in three main ways:
- Convergent Boundaries: Plates collide, causing one to subduct beneath the other.
- Divergent Boundaries: Plates move apart, creating tension.
- Transform Boundaries: Plates slide past each other, generating friction.
Key Regions of Earthquake Activity
Pacific Ring of Fire
- This horseshoe-shaped zone encircles the Pacific Ocean and accounts for about 90% of the world’s earthquakes.
- It includes major subduction zones, such as the Cascadia Subduction Zone in North America and the Japan Trench.
Mid-Atlantic Ridge
- A divergent boundary where the Eurasian and North American plates are moving apart, causing frequent but less intense earthquakes.
Himalayan Region
- A collision zone between the Indian and Eurasian plates, responsible for powerful earthquakes like the 2015 Nepal earthquake.
- Remember that earthquakes are not evenly distributed across the globe.
- They are concentrated along plate boundaries, with the most intense activity occurring at convergent and transform boundaries.
Volcanoes: Eruptions of Fire and Ash
Definition
Volcanoe
A volcano is an opening in the Earth's crust through which molten rock (lava), ashes and gases trapped under the surface erupt, often forming a hill or mountain. Volcanoes form when magma from magma chambers within the Earth’s mantle reaches the surface.
The distribution of volcanoes is closely linked to tectonic activity, with three primary settings:
- Subduction Zones: As one plate sinks beneath another, it melts and forms magma, which rises to create volcanoes.
- Rift Valleys: Diverging plates create gaps where magma can emerge.
- Hotspots: These are isolated areas where magma rises through the crust, independent of plate boundaries.
Key Regions of Volcanic Activity
Pacific Ring of Fire
- Home to about 75% of the world’s active volcanoes, including Mount St. Helens (USA) and Mount Fuji (Japan).
