Fichas
Plate Tectonics
Fichas del conjunto (29)
- 1What are fold mountains?Long relatively narrow belts of mountains, with parallel ridges and valleys. Fold mountain ranges tend to be sparsely populated.
- 2How do fold mountains form?They form where the powerful compression of two tectonic plates squeezes the layers of rocks so that the up folds form the ridges and the down folds form the valleys. This can only happen at great depths in the Earth, where the high temperatures and pressures make the rock behave as a plastic solid and allow it to be very slowly folded over long periods of time.
- 3Brief introduction to Volcanoes and EarthquakesActive volcanoes (erupted in the last 80 years)
Dormant are resting but may erupt again in the future
Extinct are dead and will not erupt again
Earthquakes occur more frequently than volcanic eruptions. - 4What is a plate?The earth's surface is made up of a series of sections known as plates. The plates include the Earth's crust and the upper part of the layer below called the mantle. The plates themselves are cold and rigid but rocks underneath them reach temperatures of more than 1300 C and flow.
- 5Why do plates move?Deep within the Earth, heat is being produced by radioactivity. The heat is not evenly distributed so there are hotter areas and colder areas. At the hotter areas, the plastic rocks in the Earth's mantle become lighter and rise, causing convection currents. These convection currents drag at the rigid plates sitting above them, causing them to move.
- 6What are destructive (convergent) plate margins?Destructive margins are places where plates move towards each other (collide). They are called destructive because oceanic plate is destroyed.
When an oceanic plate collides with a continental plate, the oceanic plate, being more dense, is forced beneath the less dense continental plate at an angle of 45 degrees. This process is known as subduction.
When the ocean floor is dragged down, it forms a long and relatively narrow ocean trench. - 7Ocean trenches?They are the deepest areas on the Earth's surface. The deep ocean floor is normally between 2000-5000 metres below sea level, but the deepest point is 11034 metres deep which is deeper than the highest mountain is high.
- 8So what happens when the oceanic plate is subducted beneath the continental plate?The friction between the two plates causes earthquakes. The earthquakes get deeper and deeper the further down the subduction zone they are.
Eventually the oceanic plate is forced so deep into the Earth that it is partially melted and becomes part of the mantle, which is then destroyed. Partial melting of the subducted plate produced magma which rises to form strato volcanoes. (these occur in the Andes)
The powerful compression of the colliding plates also crumples rocks of the continental plate and forces them up to form the fold mountain range of the Andes. - 9Other types of plate collisionsIn Japan, two oceanic plates are involved rather than one oceanic and one continental. Because there is no continental plate, there are no fold mountains. Instead, when the two oceanic plates collide, the longer plate is subducted and the rising magma produces a chain of volcanic islands known as an island arc.
- 10Other types of plate collisionsIn the Himalayas, there is a collision between two continental plates where fold mountains form and earthquakes occur. There are no volcanoes though.
- 11What are constructive (divergent) plate margins?Places where new oceanic plate is created while continental plate is neither created nor destroyed by subduction.
At constructive plate margins, the stresses within the Earth are of tension rather than compression.
The only constructive plate margins are the great ocean ridge systems. - 12What are ocean ridge systems?These ridges are huge submarine mountain ranges, which form some of the largest features on the Earth's surface.
They are mostly below sea level, but occasionally rise above it.
Beneath these great ocean ridges, there is a concentration of heat which causes partial melting. Small pockets of magma slowly collect and rise towards the Earth's surface where they cool and solidify to form new oceanic crust. This new rock forms below as well as on the surface. - 13Tension, Compression and shearing?Tension: Plates diverge and the Earth's surface is stretched and gets longer.
Compression: Plates converge and the Earth's surface is squashed and gets shorter.
Shearing: Plates slide past each other sideways and the Earth's surface does not change in length. - 14What are conservative plate margins?The plates are being conserved as neither are being created or destroyed. Shearing stress occurs at these margins and the plates slide past each other side ways. Friction between the two plates causes Earthquakes but volcanoes do not occur.
- 15Destructive Oceanic + Continental plate (Give an example, type of stress and features)Example: Andes
Type of stress: Compression
Features: Earthquakes, Fold Mountains, Volcanoes and Ocean trenches - 16Destructive Oceanic + Oceanic plate (Give an example, type of stress and features)Example: Japan
Type of stress: Compression
Features: Earthquakes, Island arcs, Volcanoes, Ocean trenches. - 17Destructive Continental + Continental Plate (An example, type of stress and features)Example: Himalayas
Type of stress: Compression
Features: Earthquakes and fold mountains - 18Constructive (Give an example, type of stress and features)Example: Mid-Atlantic Ridge
Type of stress: Tension
Features: Earthquakes, Ocean ridges and Volcanoes - 19Conservative (Give an example, type of stress and features)Example: San Andreas Fault
Type of stress: Shearing
Features: Earthquakes - 20What is a volcano?A volcano is a hole or crack in the ground through which, lava and pyroclastic material are erupted. The vent is connected to a magma chamber beneath the ground.
- 21What comes out of a volcano?Gases
The main gas is water vapor (50-80%) but there may also be emissions of Sulfur Dioxide, Hydrogen Sulfide, Nitrogen, Hydrogen and Carbon Dioxide (some of these gases are poisonous).
Liquids
Magma is molten rock material below the Earth's surface. Lava is the flows of molten rock material which have erupted onto the Earth's surface.
Solids
Ash is made up of the smallest particles, blocks of the coarsest material are much larger.
Smallest particles can be held in suspension in the air, as clouds, for a long period of time.
The particles get finer the further away they are from the volcanic vent. Because of its weight and size, the largest material is dropped nearest to the vent. More material is found close to the vent than further away. - 22Everything about shield volcanoes (where they are formed, their features, etc...)Shield Volcanoes are formed in the oceans (often at constructive plate margins).
They rise from the deep ocean floor.
They have gentle upper slopes and steeper lower slopes.
Usually have a roughly circular or oval shape in map view.
Are composed of long thing lava flow, built up over a central vent.
Have very little pyroclastic material.
Mostly formed by runny laval that flows easily down the slope away from the summit vent. The lava has low silica content and the low viscosity of the magma allows the lava to flow quickly down a gentle slope. As it cools and gets less runny, its thickness builds up on the lower slopes. - 23Stratovolcanoes (Explain their features, etc...)Stratovolcanoes
Have steeper slopes and narrower bases than shields
The steep slopes result from short, wide and very viscous lava flows that don't travel very far from the vent.
There are alternating layers of lava and pyroclastic material. Pyroclastic material can make up over half the volume of a stratovolcano.
Due to higher viscosity of magmas erupted from stratovolcanoes, they are usually more explosive and have higher silica content.
However, they have long dormant periods which makes the volcano quite dangerous since no one knows when they will erupt. - 24What are craters?Craters are circular depressions that are usually less than 1km in diameter. It is formed by an explosive ejection of material from a central vent.
- 25What are Calderas?A caldera is a huge crater caused when a volcanic cone collapses into a partly empty magma chamber after a powerful eruption.
- 26What are parasitic cones?These are smaller cones which develop on the sides of bigger volcanoes. They form when the main vent becomes blocked and magma finds another outlet.
- 27What are lava domes?Lava domes are features that often grow on the sides of stratovolcanoes. They form very viscous lava that is pale in color and has high silica content. Lava domes often collapse which leads to explosive eruptions and pyroclastic flows.
- 28What are the dangers of volcanic eruptions?Ash falls - Damages properties and can be a hazard to aircraft. Some can block the sun which affects the weather.
Pyroclastic flows - Very hot solid material can travel rapidly down valleys and slopes, it is responsible for many deaths.
Lateral blasts - Volcanoes exploding sideways can be very destructive to areas within 40km of the volcano.
Mudflows - (ash + water) travels down river valleys, since it is dense, it can wash away buildings and people.
Volcanic gases - Carbon dioxide can flow downhill, causing suffocation. Other gases that are poisonous can burn or cause lung diseases.
Acid rain - When sulfur dioxide and hydrogen sulfide are released, very large eruptions cause acid rainfall which can damage buildings and has serious effects on plants and animals.
Post-eruption and famine - The disruption to homes, roads and services caused by the effects can result in famine and disease.
Tsunami - The collapse of volcanoes in the sea can result in tsunamis.
Lava flows - They can destroy buildings but are travel too slowly to kill people. - 29What can be done to reduce the risk?Lava flow diversion - Mechanical excavators can be used to channel lava flows away from buildings. Lava flows can also be sprayed with water to cool them down and make the solidify and stop flowing.
Mudflow barriers - These are walls built across valleys to trap mudflows and protect settlements further down the valley.
Building design - Stronger roofs can stop building from collapsing when covered with ash.
Volcano monitoring - Volcanoes can be monitored to give early warning of future eruptions.
Remote sensing - Monitoring the location of the ash clouds from satellites is useful for warning aircraft
Hazard and mapping and planning - involves looking at the patterns of past eruptions to predict future ones.
Información
- Descripción
- Fichas sobre Plate Tectonics, creado por Karima Ranieri el 26/04/2015.
- Creado por
- Karima Ranieri
- Visitas
- 0
- Valoración