Tectonics, Earthquakes & Volcanoes

Question 1

1816, year without summer

Answer 1

average global temperatures decreased by 0.4 - 0.7 °C
resulted in major food shortages across the Northern Hemisphere
caused by the massive 1815 Mount Tambora (Dutch East Indies) eruption (world’s largest eruption since Hatepe eruption in 180 AD)
the eruption cloud spread across the entire globe and allowed less sun through leading to the huge drop in temperatures
high levels of tephra in the atmosphere led to unusually spectacular sunsets (evident in several painters’ (such as J. M. W. Turner) work at that time)
Crop failures led to massive famine

Question 2

Acid/dome volcano

Answer 2

Lava quickly solidifies on exposure to the air. A steep-sided convex cone is produced, as in most cases lava solidifies quickly near the crater. In one extreme case, the lava solidified on Mt. Pelee in Martinique to form a spine.

Question 3

(for a volcano) active, dormant, extinct

Answer 3

An active volcano is a volcano that is showing signs seismic or thermal activity such as smoke or an eruption. (Mt. Stromboli)
A dormant volcano is an active volcano that is not erupting, but supposed to erupt again. (Mt. Kilimanjaro))
An extinct volcano is a volcano which is not expected to erupt again. (Mt. Kenya)

Question 4

Aleutian islands

Answer 4

A chain of more than 150 mostly volcanic islands forming an island arc that separates the Bering Sea in the north from the main portion of the Pacific Ocean. Lies on the destructive Pacific and North American plate boundary.

Question 5

Alfred Wegener (1880-1930)

Answer 5

Alfred Wegener was a geophysicist and meteorologist who proposed the theory of continental drift – the idea that Earth’s continents move. Despite publishing a large body of compelling fossil and rock evidence for his theory between 1912 and 1929, it was rejected by most other scientists. It was only in the 1960s that continental drift finally became part of mainstream science.

Question 6

ash

Answer 6

Fragments of pulverized rock, minerals and volcanic glass, created during volcanic eruptions. Once in the air, ash is transported by wind up to thousands of kilometers away. Can form into an ash cloud which can block some of the sun’s rays leading to a temperature drop

Question 7

Benioff zone

Answer 7

comes after the subduction zone, where the crust is going down into the mantle.

Question 8

Caldera (acid lava)

Answer 8

Large bowl-shaped crater that forms by the collapse of a volcanic cone after an eruption. The gases which build up become so extreme that a huge explosion removes much of the former summit. Sometimes the eruptions are so violent on islands that the crater becomes flooded by the sea. (e.g. Santorini & Krakatoa)

Question 9

Cinder cone volcano (acid lava)

Answer 9

Built of ejected lava fragments. Usually small ( < 1000 ft high), have steep slopes and often form near bigger volcanoes. (e.g. Paricutin (Mexico))

Question 10

Coal in Greenland

Answer 10

On an expedition in Greenland, Wegener discovered coal. This was a curious discovery as coal is only found in places where there has been a jungle (coal is made out of residue of trees and plants from millions of years ago through combined effects of pressure and heat; it is mainly composed of carbon, oxygen and hydrogen) and since jungles are found around and close to the Equator, (and Greenland is very far from the Equator) is was very strange to find coal in Greenland). So, Greenland must have been close the equator at some point - this was evidence for Wegener’s idea of Pangea.

Question 11

Collision margin

Answer 11

Continental crust colliding with continental crust, the land is folded creating huge fold mountains. earthquakes are common at this boundary but there are no volcanoes as subduction is limited and there is usually too much material for extrusive features to form. (e.g. Himalayas & European Alps)

Question 12

Composite cone volcano

Answer 12

This is the classic shape of a volcano and is the result of alternating eruptions of lava (usually acid) and ash. (e.g. Mt. Etna, Mt. St. Helens, Mt. Fujiyama, Mt. Stromboli)

Question 13

Conservative/ Passive margin

Answer 13

2 plate slide side by side (opposite directions or in the same direction at different speeds). Crust is neither created nor destroyed. Faults and earthquakes are found at these boundaries. (e.g. San Andreas fault ( Pacific & North American plate)

Question 14

Constructive plate margin

Answer 14

Magma rises within the mantle due to convection currents. The heat weakens and cracks the crust. Magma forces its way through the crack and solidifies. A combination of the new crust and the convection currents slowly ‘pushes’ the two plates apart. New crust is constructed (hence the name ‘constructive plate boundaries) (e.g. Mid Atlantic Ridge, East Pacific Rise)

Question 15

Continental drift

Answer 15

Set forth in 1912 by Alfred Wegener, continental drift was a theory that explained how continents shift position on Earth’s surface. It also explained why look-alike animal and plant fossils, and similar rock formations, are found on different continents.

Question 16

Convection currents

Answer 16

Convection currents in the magma drive plate tectonics. Large convection currents in the mantle transfer heat to the surface, where plumes of less dense magma break apart the plates at the constructive margins, creating divergent plate boundaries. As the plates move away from the constructive margins, they cool, and the higher density basalt rocks that make up ocean crust get consumed at the ocean trenches/subduction zones. The crust is recycled back into the mantle.

Question 17

Crater lake

Answer 17

A crater lake is a depression created by a volcanic crater or caldera that is filled with water. When a volcano is no longer active, the crater or caldera may fill with water from rainfall and melting snow that may also feed the lake. A caldera is created by the collapse of a volcanic crater and the land around it. (e.g. Crater Lake, Oregon - formed by the now-collapsed volcano, Mount Mazama)

Question 18

Crust

Answer 18

The outermost solid shell of a planet

Question 19

Deep ocean trench

Answer 19

Any long, narrow, steep-sided depression in the ocean bottom. Typically form in locations where one tectonic plate subducts under another. Deepest: Mariana Trench (Pacific plate under Philippine plate)

Question 20

Destructive plate margin

Answer 20

Two plates (oceanic and continental or oceanic and oceanic) collide. One (the weaker one) falls beneath the other plate (this is the subduction zone), creating a deep trench, whilst the other will form fold mountains from stone folding and buckling as the plates collided. When the weaker plate meets the upper mantle, it will melt and mix with the magma. Since it is now a mixture of substances from both the crust and mantle, it is lighter and will rise in the form of plutons under the fold mountains, creating volcanoes. This is why it is extremely common to find volcanoes along a destructive boundary. However, most of the rising magma will actually never make it to the surface, sometimes forming batholiths (e.g. Sugar Loaf in Rio de Janeiro). As the weaker plate moves down, it also pulls down the edge of the other plate causing earthquakes since rock does not move along rock smoothly. This will also lead to an increase in tension until it is released when the stronger plate flicks back up usually causing a tsunami.

Question 21

Disease

Answer 21

Disease can spread very easily after an earthquake due to a lack of clean water and medical facilities

Question 22

Drop, cover, hold

Answer 22

If one is indoors during an earthquakes, these are appropriate actions to reduce risk of injury and death.

Question 23

epicentre

Answer 23

The point on the Earth’s surface that is directly above the earthquake focus (the point where an earthquake or underground explosion originates).

Question 24

fissure volcano

Answer 24

Liquid flows (usually) from elongated fractures or cracks on the slope of a volcano. Common where plates move apart (constructive boundary). The basalt (solidifies lava) may form large plateaus (new crust). Basic lava. Common in Iceland (e.g. Eyjafjallajökull) and the Giants Causeway in Ireland.

Question 25

Focus

Answer 25

The point inside the crust where pressure is released causing an earthquake.

Question 26

fold mountains

Answer 26

a range of high mountains formed by two plates moving together at a collision or destructive margin

Question 27

hot spot

Answer 27

An area in the Earth’s mantle where a column of magma rises and melts through the crust leading to volcanic activity. As new magma continues to rise and solidify, islands can be made. It is common to find a chain of islands (e.g. Hawaii) with the biggest ones closer to the hotspot and the smaller ones further from it. This is due to the movement of the plate; so if the hotspot forms an island and the plate moves, it will start forming a new one next to the old one. The older islands get eroded by the ocean, making them smaller.

Question 28

island arc

Answer 28

a curving line of islands formed by volcanic activity at a destructive plate boundary (e.g. Aleutian islands)

Question 29

lava

Answer 29

molten rock (magma) ejected onto the Earth’s surface by volcanic activity. Two types: basaltic/basic - fluid, pure magma, not mixed with anything else (e.g. Hawaii); and andesitic/acid - viscous, comes from subduction zone (e.g. Andes)

Question 30

mantle

Answer 30

the part of the Earth’s structure between the crust and the core

Question 31

plate tectonics

Answer 31

the theory that the surface of the Earth is divided into a series of plates, consisting of continental and oceanic crust.

Question 32

Richter scale

Answer 32

the scale used to measure the magnitude of earthquakes

Question 33

Fukushima (2011)

Answer 33

On March 11, 2011, a magnitude-9 earthquake shook northeastern Japan. Radioactive water was recently discovered leaking from the Fukushima Daiichi Nuclear Power Plant, which suffered a level 7 nuclear meltdown after the tsunami. Japan relies on nuclear power, and many of the country’s nuclear reactors remain closed because of stricter seismic safety standards since the earthquake.

Question 34

global dimming

Answer 34

The decrease in the amounts of solar radiation reaching the surface of the Earth. Can be caused by the ash cloud of a volcanic eruption and lead to severe drop in temperatures and food shortages.

Question 35

Gondwanaland

Answer 35

The southern supercontinent Gondwana (originally Gondwanaland) included most of the landmasses which make up today’s continents of the southern hemisphere, including Antarctica, South America, Africa, Madagascar, India, Arabia, Australia-New Guinea and New Zealand.

Question 36

Haiti (2010)

Answer 36

On January 12, 2010, an earthquake registering a 7.0 on the Richter scale struck the country of Haiti, a few miles outside the capital of Port-Au-Prince. This devastating natural disaster killed over 200,000 and left over 600,000 injured or homeless, struggling to find the basic resources needed for survival. The earthquake also drastically changed the political, economical and ecological landscapes of Haiti, causing the already fragile government to virtually collapse. The lack of leadership during the time of crisis led to the reliance on foreign aid for almost all needed resources. Tent camps sprung up all over the country for people to live in during their transient living state.

Question 37

Harry Truman

Answer 37

He was the owner and caretaker of Mount St. Helens Lodge at Spirit Lake, located at the south end of Spirit Lake at the foot of the mountain in the danger zone at the time of the eruption. He came to brief fame in the months preceding the volcano’s 1980 eruption after he stubbornly refused to leave his home despite evacuation orders, and he is presumed to have been killed in the eruption.

Question 38

Hawaii

Answer 38

The northwest moving Pacific Plate has moved across the ‘hot spot’ that created the Hawaiian Islands for millions of years. This movement has left the northwest trending island chain we call Hawaii. As islands move northwest, away from the ‘hot spot,’ they begin to erode and become volcanically inactive. Over time the island may erode so much it is no longer an island but an underwater seamount.

Question 39

inner core

Answer 39

The Earth’s inner core is the Earth’s innermost part and according to seismological studies, it has been believed to be primarily a solid ball with a radius of about 1,220 km. It is composed of an iron–nickel alloy and some light elements. The temperature at the inner core boundary is approximately 5400 °C.

Question 40

Japan 2011

Answer 40

Severe natural disaster that occurred in northeastern Japan on March 11, 2011. The event began with a powerful earthquake off the northeastern coast of Honshu, Japan’s main island, which caused widespread damage on land and initiated a series of large tsunami waves that devastated many coastal areas of the country, most notably in the Tōhoku region (northeastern Honshu). The tsunami also instigated a major nuclear accident at a power station along the coast.

Question 41

Jigsaw fit of continents

Answer 41

Looking at a world map in 1910, Wegener noticed how the coastlines of eastern South America and western Africa seemed to fit together, rather like jigsaw pieces.

Question 42

La Palma

Answer 42

Scientists have warned that a massive slab of rock will break off the La Palma volcano, crashing into the Atlantic Ocean and causing a mega-tsunami which would wipe away America’s east coast population.

Question 43

lahar/mudflow

Answer 43

A lahar is a form of a mudslide, triggered most often by a volcanic eruption, which flows down the mountain. As the lahar travels down the mountain, other debris such as rocks, logs, and trees become part of the fast moving mudslide. A volcano does not always have to erupt for a lahar to form. Sometimes heavy rains falling on old, loose volcanic ash or a crater dam failure can also cause a lahar.

Question 44

Laurasia

Answer 44

Laurasia (it included North America, Europe, and Asia (except peninsular India)) was the more northern of two supercontinents (the other being Gondwana) that formed part of the Pangaea supercontinent around 335 to 175 million years ago.

Question 45

Lava flow

Answer 45

Streams of molten rock that pour or ooze from an erupting vent. Lava is erupted during either nonexplosive activity or explosive lava fountains.

Question 46

looting

Answer 46

possible secondary effect of an earthquake, in state of chaos, it is easier for thieves to loot (shops are abandoned, no police…)

Question 47

Mesosaurus

Answer 47

Remains of Mesosaurus, a freshwater crocodile-like reptile that lived during the early Permian (between 286 and 258 million years ago), are found solely in Southern Africa and Eastern South America. It would have been physiologically impossible for Mesosaurus to swim between the continents. This suggests that South America and Africa were joined during the Early Permian.

Question 48

Mid Atlantic Ridge

Answer 48

A mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South American Plate in the South Atlantic. The ocean ridge rises to between 2 to 3 km above the ocean floor, and has a rift valley at its crest marking the location at which the two plates are moving apart.

Question 49

mid ocean ridge

Answer 49

Places in the Earth’s system of tectonic plates where new crust forms and the plates move away from one another. Powered by magma rising and falling in the mantle, these undersea mountain ranges are formed by numerous eruptions of basalt lava along their length. Because in almost all cases the eruptions take place deep below the ocean surface, mid-ocean ridges were only properly discovered in the 1950s.

Question 50

Modified Mercalli

Answer 50

The intensity scale consists of a series of certain key responses such as people awakening, movement of furniture, damage to chimneys, and finally - total destruction.

Question 51

Mt. St. Helens

Answer 51

An active stratovolcano located in Skamania County, Washington. This volcano is well known for its ash explosions and pyroclastic flows. Mount St. Helens is most notorious for its major 1980 eruption, the deadliest and most economically destructive volcanic event in the history of the United States.

Question 52

Nazca vs. South American

Answer 52

Destructive plate margin, Peru-Chile Trench, Andes

Question 53

Nepal 2015

Answer 53

Severe earthquake (7.8 Richter) that struck near the city of Kathmandu in central Nepal on April 25, 2015. About 9,000 people were killed, many thousands more were injured, and more than 600,000 structures in Kathmandu and other nearby towns were either damaged or destroyed.

Question 54

Noah Tsunamis sphere

Answer 54

A spherical earthquake and tsunami shelter “Noah” made of fiber enforced plastic. It keeps water out and its occupants afloat, all the while protecting them from floating debris. Its bright yellow colour was designed to attract the attention of rescuers.

Question 55

outer core

Answer 55

The outer core of the Earth is a fluid layer about 2,300 km thick and composed of mostly iron and nickel that lies above Earth’s solid inner core and below its mantle.

Question 56

P wave (primary wave)

Answer 56

This is the fastest kind of seismic wave, and, consequently, the first to ‘arrive’ at a seismic station. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and pulls the rock it moves through just like sound waves push and pull the air.

Question 57

S wave (secondary wave)

Answer 57

The second wave you feel in an earthquake. An S wave is slower than a P wave and can only move through solid rock, not through any liquid medium. It is this property of S waves that led seismologists to conclude that the Earth’s outer core is a liquid. S waves move rock particles up and down, or side-to-side perpendicular to the direction that the wave is traveling in

Question 58

L waves (Love waves)

Answer 58

It’s the fastest surface wave and moves the ground from side-to-side. Confined to the surface of the crust, Love waves produce entirely horizontal motion.

Question 59

R waves (Rayleigh waves)

Answer 59

A Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Because it rolls, it moves the ground up and down, and side-to-side in the same direction that the wave is moving. Most of the shaking felt from an earthquake is due to the Rayleigh wave, which can be much larger than the other waves.

Question 60

paleo magnetism

Answer 60

The study of magnetic rocks and sediments to record the history of the magnetic field. One of the strongest pieces of evidence for plate tectonics has been paleomagnetism. Evidence has shown, for example, that some rocks in Alaska have magnetic minerals oriented in such a way that they must have been laid down at or near the equator. The fact that they are now at 70° north latitude suggests strongly that the plate on which they are riding must have migrated a very long distance during Earth history. Paleomagnetism can also be used to match up land masses that are now separated from each other, but which must once have been joined. One of the most remarkable successes of paleomagnetism has been in the study of sea floor spreading.

Question 61

Pangaea

Answer 61

About 300 million years ago, Earth didn’t have seven continents, but instead one massive supercontinent called Pangaea.

Question 62

plate

Answer 62

When we talk about tectonic or lithospheric plates, we mean the sections into which the lithosphere is cracked. The surface of the Earth is divided into 7 major and 8 minor plates.

Question 63

primary effects

Answer 63

Primary effects occur as a direct result of the ground shaking. These include buildings collapsing, roads and bridges being destroyed and railway lines being buckled.

Question 64

pumice

Answer 64

Extremely porous igneous rock that forms during explosive volcanic eruptions. Many specimens have a high enough porosity that they can float on water until they slowly become waterlogged.

Question 65

pyroclastic flow

Answer 65

A dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing at great speed.

Question 66

San Andreas fault

Answer 66

The San Andreas Fault is the conservative boundary between the Pacific Plate and the North American Plate. The presence of the San Andreas fault was brought dramatically to world attention on April 18, 1906, when sudden displacement along the fault produced the great San Francisco earthquake and fire.

Question 67

sea floor spreading

Answer 67

Seafloor spreading is a geologic process in which tectonic plates—large slabs of Earth’s lithosphere—split apart from each other. Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor. Eventually, the crust cracks. Hot magma fueled by mantle convection bubbles up to fill these fractures and spills onto the crust. This bubbled-up magma is cooled by frigid seawater to form igneous rock. This rock (basalt) becomes a new part of Earth’s crust.

Question 68

secondary effects

Answer 68

Secondary effects occur as a result of the primary effects, eg tsunamis or fires due to ruptured gas mains.

Question 69

seismic waves

Answer 69

Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.

Question 70

seismometer

Answer 70

instrument used to measure the direction, intensity, and duration of earthquakes by measuring the actual movement of the ground.

Question 71

sept 1st in Japan

Answer 71

Earthquake preparedness day

Question 72

shield volcano

Answer 72

a broad domed volcano with gently sloping sides, characteristic of the eruption of fluid, basaltic lava (e.g. Mauna Loa, Erta Ale)

Question 73

subduction zone

Answer 73

the region at a destructive plate boundary where one plate subducts/dives under the other

Question 74

Tambora (1815)

Answer 74

On 10 April 1815, Tambora produced the largest eruption known on the planet during the past 10,000 years. The volcano erupted more than 50 cubic kilometers of magma. Caldera collapse at the end of the eruption destroyed 30 km3 of the mountain and formed a 6 km wide and 1250 m deep caldera. The eruption produced global climatic effects and killed more than 100,000 people, directly and indirectly. “The Year without a Summer” (ash cloud)

Question 75

tsunami

Answer 75

A tsunami is a series of waves caused by earthquakes or undersea volcanic eruptions

Question 76

Yellowstone

Answer 76

Most of Yellowstone National Park sits inside three overlapping calderas. The shallow, bowl-shaped depressions formed when an underground magma chamber erupted at Yellowstone. Fear of of super eruption which could devastate a lot of life on Earth.