Named examples: Earthquakes and volcanoes

A named place with a date or figure, linked to your point, turns a general answer into a developed one.

This lesson collects the 29 named examples from the lessons in this chapter, so you can revise them in one place. Each one is also a recall card below, so you can save the whole set and review it before an exam.

Earth's layers and tectonic plates (plate tectonics): Crust and plate thickness (USGS); Mantle and core (USGS).

Why tectonic plates move (plate tectonics): Nazca Plate and the Peru-Chile Trench.

Seafloor spreading (plate tectonics): Mid-Atlantic Ridge spreading rate (USGS); Iceland, where the ridge reaches land.

Magnetic striping (plate tectonics): 1950s ocean surveys (USGS).

Plate boundaries (plate tectonics): Divergent, ocean: Mid-Atlantic Ridge; Divergent, continent: East African Rift; Ocean meets continent: Andes; Ocean meets ocean: Mariana Trench and Islands; Continent meets continent: Himalayas; Transform: San Andreas Fault.

Earthquakes and magnitude: Tohoku, Japan, 2011; Haiti and Chile, 2010.

Magma and eruption styles: Mount Pinatubo, Philippines, 1991; Kilauea, Hawaii, 2018.

Where earthquakes and volcanoes occur: Pacific Ring of Fire; Hawaii and Iceland; Indian Ocean tsunami, 2004.

Earthquake hazards: Tohoku, Japan, 2011; Christchurch, New Zealand, 2011; Nepal, 2015.

Lava, pyroclastic flows and landslides: Mount Merapi, Indonesia, 2010; Mount St Helens, USA, 1980.

Ash, gases and lahars: Nevado del Ruiz, Colombia, 1985; Eyjafjallajokull, Iceland, 2010; Lake Nyos, Cameroon, 1986.

Benefits of volcanic areas: Iceland; Java, Indonesia.

To use a case, name the place or organisation, give its date or a figure, then say what it shows about the question. One developed case earns more than a list of names.

Crust and plate thickness (USGS)

Under the oceans the crust is only about 5 km thick. Under the continents it averages about 30 km. The lithosphere, which forms the plates, is at least 80 km thick over much of Earth.

Mantle and core (USGS)

The mantle is about 2,900 km thick. Below it, the liquid outer core is about 2,200 km thick and the solid inner core about 1,250 km thick.

Nazca Plate and the Peru-Chile Trench

Off South America, the ocean Nazca Plate sinks under the South American Plate along the Peru-Chile Trench. The sinking slab helps pull the Nazca Plate east towards the trench.

Mid-Atlantic Ridge spreading rate (USGS)

The Mid-Atlantic Ridge spreads at an average of about 2.5 cm a year, or 25 km in a million years. So the Atlantic Ocean is slowly getting wider.

Iceland, where the ridge reaches land

Iceland sits across the Mid-Atlantic Ridge. Here the ridge rises above sea level, so the rift between the North American and Eurasian Plates can be seen on land.

1950s ocean surveys (USGS)

From the 1950s, scientists towed magnetometers, adapted from devices built in the Second World War to find submarines, across the ocean floor. They found stripes of normal and reversed rock in rows on both sides of the mid-ocean ridges.

Divergent, ocean: Mid-Atlantic Ridge

The North American and Eurasian Plates move apart at about 2.5 cm a year (USGS). New ocean crust forms along the ridge, which runs through Iceland.

Divergent, continent: East African Rift

The African Plate is splitting into the Nubian and Somali Plates, by only a few millimetres a year. The crust stretches and drops into a rift valley, with faults and volcanoes.

Ocean meets continent: Andes

The ocean Nazca Plate sinks under the South American Plate at the Peru-Chile Trench. This built the volcanic Andes. Here, on 22 May 1960, the Valdivia earthquake in Chile reached magnitude 9.5, the largest ever recorded (USGS).

Ocean meets ocean: Mariana Trench and Islands

The Pacific Plate sinks under the Philippine Sea Plate. The Challenger Deep at the trench's southern end is nearly 11,000 m deep (USGS). Volcanoes on the overriding plate form the Mariana Islands, an island arc.

Continent meets continent: Himalayas

India collided with Asia about 40 to 50 million years ago. The crust crumpled into the Himalayas, which still rise by more than 1 cm a year (USGS). There is no chain of volcanoes.

Transform: San Andreas Fault

In California, the Pacific Plate has slid past the North American Plate for about 10 million years, at an average of about 5 cm a year (USGS). The fault makes earthquakes but no volcanoes.

Tohoku, Japan, 2011 (Earthquakes and magnitude)

A magnitude 9.0 earthquake struck off north-east Japan when the Pacific Plate slipped under the plate carrying Japan. It was one of the largest earthquakes ever recorded.

Haiti and Chile, 2010

Haiti's magnitude 7.0 earthquake killed more than 220,000 people by UN estimates. Chile's magnitude 8.8 earthquake released about 500 times more energy but killed fewer than 800. Magnitude alone does not decide the damage.

Mount Pinatubo, Philippines, 1991

Sticky, gas-rich magma produced one of the largest eruptions of the 20th century. Its ash column rose about 35 km high.

Kilauea, Hawaii, 2018

Runny basaltic lava flowed out gently rather than exploding, but the flows destroyed over 700 homes.

Pacific Ring of Fire

Most of the world's active volcanoes and large earthquakes lie around the edge of the Pacific Ocean, along plate boundaries from Chile to Japan and Indonesia.

Hawaii and Iceland

Hawaii's volcanoes sit over a hotspot in the middle of the Pacific Plate. Iceland lies on the Mid-Atlantic Ridge, where two plates move apart.

Indian Ocean tsunami, 2004

An earthquake off Sumatra, Indonesia, sent a tsunami that killed people as far away as Sri Lanka, India and Somalia, thousands of kilometres from the source.

Tohoku, Japan, 2011 (Earthquake hazards)

The earthquake set off a tsunami that left about 18,000 people dead or missing. The tsunami also flooded the Fukushima Daiichi nuclear plant, causing a nuclear accident.

Christchurch, New Zealand, 2011

The earthquake of 22 February 2011 killed 185 people. Most died when two office blocks collapsed: 115 in the CTV building and 18 in the PGC building. Shaking also turned wet, sandy ground to liquid (liquefaction), so homes in the eastern suburbs tilted and sank and roads and pipes broke.

Nepal, 2015

A magnitude 7.8 earthquake killed about 9,000 people and set off landslides and an avalanche on Mount Everest.

Mount Merapi, Indonesia, 2010

Pyroclastic flows from Merapi killed more than 300 people and forced hundreds of thousands to evacuate.

Mount St Helens, USA, 1980

The volcano's north side collapsed in the largest landslide ever recorded, releasing a sideways blast that flattened forests.

Nevado del Ruiz, Colombia, 1985

A small eruption melted snow and ice. The resulting lahar buried the town of Armero, killing about 23,000 people.

Eyjafjallajokull, Iceland, 2010

Ash from this eruption closed much of Europe's airspace for days, and about 100,000 flights were cancelled.

Lake Nyos, Cameroon, 1986

A sudden release of carbon dioxide from a volcanic lake suffocated about 1,700 people.

Iceland

About 90% of homes in Iceland are heated with geothermal hot water from underground.

Java, Indonesia

Millions of farmers live on the slopes of volcanoes such as Merapi because weathered volcanic ash makes very fertile soil.