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Description
Flashcards by Nicola Bywater, updated more than 1 year ago
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Created by Nicola Bywater
almost 12 years ago
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| Question | Answer |
| Constructive | Plates move away from each other and basaltic lava fills the spaces creating new crust |
| Another name for constructive margin | Diverging Sea floor spreading |
| Oceanic constructive margin feature and description | Ocean ridges, - The longest, continuous uplifted features on the surface of the planet - Total of 60,000km and up to 3km above sea level |
| Example of ocean ridge and the plates involved | Mid-Atlantic Ridge, Eurasian and South African plates move away from North and South America |
| Where and how is there volcanic activity at a constructive plate margin? | - Occurs alongside the ridge, with initial submarine volcanoes which grows above sea levels with persistent eruptions - It may form volcanic islands like Sutsey, Iceland |
| Why do oceanic, constructive volcanoes have fairly gentle sides? | Due to low viscosity lava travelling a long way before cooling |
| What type of seismic action is found at oceanic, constructive margins? | Shallow focus earthquakes |
| Features and processes in continental, constructive margins | - Rift Valleys - Spreading beneath major land masses causes heating and updoming of the earths crust which leads to fracturing and rifting - The sides of the rifts move apart and central sections drop down for the valleys |
| Where are volcanoes found at Rift Valleys and give an example | - At the side of the Valleys - Mt. Kilimanjaro |
| Example of a Rift Valley and its characteristics | Great African Rift Valley - Somali and Nubian Plates as the African plate splits - 4000km long from Mozambique to the red Sea, 50km wide - Red Sea is becoming the Worlds newest ocean |
| Define a destructive margin | Two plates move towards each other, destroying crust |
| Another name for a destructive margin | Convergent |
| Oceanic - Continental destructive margin type and description | Subduction - Denser oceanic plate underneath the continental, subducted into aesthenosphere |
| What features are found at an oceanic-continental destructive margin? | Volcanoes, Earthquakes, Deep sea trenches, Rift Valleys, Tsunamis |
| Describe a volcano at a oceanic-continental subduction zone | Viscous nature of lava creating andesitic volcanoes (composite and explosive) |
| What is an Andestic Volcano? | A volcano made from viscous lava which is explosive, composite and complex in its nature |
| How are Island Arcs formed? Give an example of this feature | When magma erupts offshore, away from the plate boundary. Japan is an example |
| How are earthquakes triggered at an oceanic- continental destructive margin? | Pressure increases along the line of focus, they can be shallow, deep or intermediate focus which happen both inland and offshore |
| What is this known as? The further the rock descends the hotter the surroundings become, the plate melts into the magma due to the heat from the friction | Benioff zone |
| Give a detailed example of an oceanic - continental destructive margin and an example of its features | Nazca and South American Plates Andes mountain range Peru Chile deep ocean trench - 8km deep |
| How does a volcano form at an oceanic-continental destructive plate boundary? | Melted rock from the benioff zone is less dense than its surrounding aesthenosphere so begins to rise up through fissures, it burns through overlying rock and eventually reaches the surface in the form of a volcano |
| Fold mountains at oceanic - continental destructive margins | The folding of the continental crusts sediments on the edge of the continental shelf and land masses are deformed by folding and faulting, forms this feature |
| Which plate is subducted at an oceanic - oceanic subduction zone | Marginally denser or faster crust |
| Name and describe all the features associated with a oceanic-oceanic destructive margin | - Shallow, deep focus earthquakes (2004 Indonesian - Australian beneath Eurasian) - Offshore volcanic activity (Marina Islands) and deep ocean trenches (Marinas Trench - 11km deep) - Pacific and Philipine trench - Tsunamis (Indian Ocean, 2004) |
| The name of a continental-continental destructive boundary | Collision zone because no subduction takes place, due to their buoyancy and being less dense |
| Give features associated with collision boundaries and examples | - Fold mountains with deep lithospheric roots as sediments are forced up (Himalyas, 40 million years ago - Indian and Eurasian and Sea of Tethys) - Shallow focus earthquakes (Sichuan, 2008 - caused 80000 deaths) |
| What is a conservative boundary? | Transform faults where crust is neither produced or destroyed as the plates slide horizontally past each other |
| What seismic and volcanic events occur at conservative plate boundaries? | - No volcanic activity due to no subduction - Shallow focus earthquakes as there are stresses between the plate edges as sections of plates rub past each other |
| Give an example of a conservative plate boundary | San Andreas Fault - California USA, Plates moving North West - Pacific (6cmpy) and North American (1cmpy) |
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