Tectonics Facts Flashcards
What is an ocean ridge caused by? And how does this lead to the submarine volcanoes?
As two plates pull apart they form a weaker zone in the crust
The weaker zone is exposed to high temperatures which causes it to expand and stretch - forming a ridge
The split in the crust provides a lower pressure zone where more liquid lava can erupt to form submarine volcanoes
Continued eruptions may cause volcanoes to develop at the surface
Give an example of an island/country formed by an ocean ridge?
Iceland
Where are ocean trenches found (boundary) and what is an example of one?
Oceanic/oceanic subduction plate margins
Mariana Trench
What are some examples of fold mountains?
The Himalayas
The Rockies
The Andes
The Alps
What are island arcs?
Curved chains of volcanic islands located at a plate margin
Caused by destructive subduction
What is an example of an island arc?
Japanese Islands
- where North American, Pacific, Eurasian and Phillipine plates come together
What are major extrusive landforms? Examples
Molten rock that reaches the surfaces
- Fissures
- Shield volcanoes
- Acid/dome volcanoes
- Ash and cinder cone
- Composite cones
- Calderras
What is a fissure? Example?
Where two plates move apart and lava is released through fissures rather than central vent
- Giant’s Causeway, Northern Ireland
What is a shield volcano? Example?
Wide volcano with gently sloping sides with runny lava
- Mauna Loa
What is an acid/dome volcano? Example?
Steep sided volcano where lava has solidified near the crater
- Mt Pelee, Martinique
What is an ash and cinder cone? Example?
Ash and cinders build up layers to form a symmetrical cone with slightly concave sides
- Paricutin, Mexico
What is a composite cone? Example?
Formed from alternating gentle eruptions releasign acidic lava, steep sided
- Mt Etna, Sicily
What is a calderra? Example?
Massive crater, magma chamber below volcano may be cleared out by gas build up being released
- Mt Pinatubo, Phillappines
What are the 6 types of eruption and their features?
Icelandic - lava flows gently from long fissure
Hawaiian - lava emitted gently from a vent
Strombolian - small but frequent eruptions
Vulcanian - violent and less frequent
Peelean - violent eruption accompanied by pyroclastic flow
Plinian - large amounts of lava and pyroclastic
What is a minor extrusive landforms? Examples
Smaller
- Geysers
- Hot springs
- Mud pots
- Solfatara
- Fumaroles
What’s a geyser? Example?
Formed when water in the lower crust is heated by rocks which increases pressure that causes steam to explode on surface
- Old Faithful, Yellowstone
What is a hot spring? Example?
Formed when water seeps into underground hot volcanic rocks which then flows back to the Earth’s surface
- Grand Prismatic Spring, Yellowstone
What is a mud pot? Example?
Formed in geothermal areas where water is in short supply, water rises to surface which boils mud and clay
- Fountain Paint Pots, Yellowstone
What is a solfatara?
Volcanic vent/fissure giving off vapours of sulphurous gases
What is a fumarole?
Where super heated water turns to steam, pressure dropping when it hits the surface
What is an intrusive landform? Examples
Molten rock injected into crust
- Batholiths, dikes, sills, plutons and laccoliths
What is a batholith? Example?
Large deep seated mass of magma that cools to form coarse grained rock
- Cornubian Batholith, Cornwall
What is a sill? Example?
Horizontal intrusion along the bedding planes with vertical cooling cracks that contract and crack more
- Whin Sill, North Yorkshire
What is a dyke? Example?
Vertical intrusion with horizontal cooling cracks
- Kildonan, Arran, Scotland
What are the 3 types of seismic waves and their features?
Primary: fastest, shake backwards and forwards, move through solids and liquids
Secondary: slower, move sideways shaking earth at right angles to direction of travel, do more damage than P waves
Surface: near the surface, move the slowest, most destructive
What do surface waves include?
Love waves: sideways movement
Rayleigh waves: up and down movement
What are the two scales that measure magnitude and what do they do?
Richter scale: logarithmic scale with each unit representing a 10 fold increase n strength (x10)
Moment magnitude: Developed to succeed the Richter Scale and is more accurate for quakes above 3.5
What’s the Mercalli scaled?
Measures damage of seismic events
What are the 4 steps of a tsunami?
Tsunamigenesis - fault, displacement, waves radiate from epicentre
Tsunami draw back - ocean sucked back
Tsunami run up - approaching wave and rise in sea level
Tsunami land fall- movement of contact, destruction, inundation
What are the geomorphological effects of earthquakes?
- Ground shaking
- Landslides
- Avalanches
- Tsunamis
What are the factors affecting the severity of an earthquake?
- Magnitude
- Distance decay (distance from epicentre)
- Underlying geology
- Human factors (population density, economic stance, infrastructure, monitoring/preparation)
What are the secondary effects of earthquakes?
- Tsunamis
- Landslides and avalanches
- Liquefaction
What is liquefaction?
Where the ground becomes liquid like- shaking reduces pore water pressure, the soil becomes weak and falls and the groundwater carries it to the surface where its liquified
What does the human impacts of earthquakes depend on?
- Pop density
- Distance from epicentre
- Economic development
- Stability
- International cooperation
What are seismographs and how can they be used?
- They measure and record shock waves created by earthquakes
- They locate and measure the size of waves and are used in data analysis to establish patterns of activity
- This can help with future prediction and planning
What are intra plate vents?
Areas not near plate margins where earthquakes occur
- Earthquakes happen due to lines of weakness being reactivated by crustal stress or tremors
