1.2C Impacts on Hazards
Physical processes impact on the magnitude and type of volcanic eruption, and earthquake magnitude and focal depth.
Constructive margins:
Eruptions are small and effusive, as the erupted basalt lava has a low gas content and high viscosity. Earthquakes are shallow, less than 60 km deep, and have low magnitudes of under 5.0.
Oceanic-Oceanic: Minor, shallow earthquakes.
Continent-Continent: Basaltic volcanoes and minor earthquakes.
Convergent Margins
Destructive Margins
Earthquakes at subduction zones occur at a range of focal depths from 10 km to 400 km, following the line of the subducting plate. This is called the Benioff Zone, and it can yield very large earthquakes up to magnitude 9.0. The descending plate begins to melt at depth by a process called wet partial melting. This generates magma with a high gas and silica content, which erupts with explosive force.
Collision zones
Collision zones are cut by huge thrust faults that generate shallow, high-magnitude earthquakes such as in Kashmir in 2005 and Nepal in 2015.
Oceanic-Oceanic: Frequent earthquakes, and violent eruptions from curving chain of volcanic islands.
Continent-Continent: Infrequent major earthquakes distributed over a wide area.
Oceanic-Continent: Frequent large earthquakes and violent eruptions.
Conservative Margins
Earthquakes along conservative boundaries often have shallow focal depths, meaning high magnitude earthquakes can be very destructive. Volcanic activity is absent.
Oceanic-Continent: Frequent, shallow earthquakes, but no volcanic activity.