Tectonics, Earthquakes & Volcanoes Flashcards
1816, year without summer
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
Acid/dome volcano
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.
(for a volcano) active, dormant, extinct
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)
Aleutian islands
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.
Alfred Wegener (1880-1930)
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.
ash
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
Benioff zone
comes after the subduction zone, where the crust is going down into the mantle.
Caldera (acid lava)
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)
Cinder cone volcano (acid lava)
Built of ejected lava fragments. Usually small ( < 1000 ft high), have steep slopes and often form near bigger volcanoes. (e.g. Paricutin (Mexico))
Coal in Greenland
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.
Collision margin
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)
Composite cone volcano
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)
Conservative/ Passive margin
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)
Constructive plate margin
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)
Continental drift
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.
Convection currents
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.
Crater lake
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)
Crust
The outermost solid shell of a planet
Deep ocean trench
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)
Destructive plate margin
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.
Disease
Disease can spread very easily after an earthquake due to a lack of clean water and medical facilities
Drop, cover, hold
If one is indoors during an earthquakes, these are appropriate actions to reduce risk of injury and death.
epicentre
The point on the Earth’s surface that is directly above the earthquake focus (the point where an earthquake or underground explosion originates).
fissure volcano
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.
Focus
The point inside the crust where pressure is released causing an earthquake.
fold mountains
a range of high mountains formed by two plates moving together at a collision or destructive margin
hot spot
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.
island arc
a curving line of islands formed by volcanic activity at a destructive plate boundary (e.g. Aleutian islands)
lava
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)
mantle
the part of the Earth’s structure between the crust and the core
plate tectonics
the theory that the surface of the Earth is divided into a series of plates, consisting of continental and oceanic crust.
Richter scale
the scale used to measure the magnitude of earthquakes
Fukushima (2011)
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.
global dimming
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.
Gondwanaland
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.
Haiti (2010)
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.
Harry Truman
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.
Hawaii
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.
inner core
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.
Japan 2011
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.
Jigsaw fit of continents
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.
La Palma
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.
lahar/mudflow
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.
Laurasia
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.
Lava flow
Streams of molten rock that pour or ooze from an erupting vent. Lava is erupted during either nonexplosive activity or explosive lava fountains.
looting
possible secondary effect of an earthquake, in state of chaos, it is easier for thieves to loot (shops are abandoned, no police…)
Mesosaurus
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.
Mid Atlantic Ridge
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.
mid ocean ridge
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.
Modified Mercalli
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.
Mt. St. Helens
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.
Nazca vs. South American
Destructive plate margin, Peru-Chile Trench, Andes
Nepal 2015
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.
Noah Tsunamis sphere
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.
outer core
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.
P wave (primary wave)
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.
S wave (secondary wave)
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
L waves (Love waves)
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.
R waves (Rayleigh waves)
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.
paleo magnetism
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.
Pangaea
About 300 million years ago, Earth didn’t have seven continents, but instead one massive supercontinent called Pangaea.
plate
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.
primary effects
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.
pumice
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.
pyroclastic flow
A dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing at great speed.
San Andreas fault
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.
sea floor spreading
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.
secondary effects
Secondary effects occur as a result of the primary effects, eg tsunamis or fires due to ruptured gas mains.
seismic waves
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.
seismometer
instrument used to measure the direction, intensity, and duration of earthquakes by measuring the actual movement of the ground.
sept 1st in Japan
Earthquake preparedness day
shield volcano
a broad domed volcano with gently sloping sides, characteristic of the eruption of fluid, basaltic lava (e.g. Mauna Loa, Erta Ale)
subduction zone
the region at a destructive plate boundary where one plate subducts/dives under the other
Tambora (1815)
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)
tsunami
A tsunami is a series of waves caused by earthquakes or undersea volcanic eruptions
Yellowstone
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.
