HKDSE Geography/M1/Distribution of Tectonic Hazards

Tectonic hazards are not equally distributed over the earth's surface.

Plate Boundary Types and Hazard Occurrence

Most hazards occur at plate boundaries, with some exceptions we will see in the next chapter.

	Earthquakes	Volcanic Eruptions	Tsunamis
Constructive	Somewhat rare	Common	Somewhat rare
Destructive	Common	Common*	Common*
Conservative	Common	None	None

*Mostly at the Circum-Pacific Belt.

Note that:

• Volcanic eruptions are common in constructive plate boundaries, but they have less destructive power because the overlying seawater and the seabed suppresses the outpouring of magma.
• Tsunamis are most active at destructive plate boundaries and are mostly concentrated along coastal areas around the Pacific Ocean; however, they have occurred in the Atlantic and the Indian Oceans as well. The Indian Ocean tsunami in 2004 is an important example.

Two Belts

Two regions face serious tectonic hazards:

• Circum-Pacific Belt: It runs around the Pacific Ocean. Most of the earth's volcanoes and sources of earthquakes and tsunamis are found here. With reference to volcanoes, it is known as the Pacific Ring of Fire because of the ring-like spatial distribution of volcanoes here.
• Alpine-Himalayan Belt: It runs from the Alps to the Himalayas, and earthquakes are very active here.