Tectonic Processes and Hazards - Key terms and Ideas Flashcards
How are tectonic hazards distrubuted?
Most tectonic hazards are located on or near tectonic plate margins and occur due to movement of plates at these margins. Despite this, some tectonic hazards occur in the absence of a plate margin for example at volcanic hotspots.
What are the types of plate margin?
Conservative
Divergent (constructive)
Convergent (destructive)
Collision
Describe and give examples of conservative plate margins
Plates move laterally and rub against eachother. This creates friction and occassionally causes plates to become stuck on eachother - producing huge tension. When the plates become dislodged, the tension is relieved and huge amouns of energy are released in the form of an earthquake. Earthquakes at conservative margins typically have shallow hypocenters meaning less energy is dissipated before it reaches Earth’s surface, resulting in more violent shaking.
Examples include:
San Andreas Fault
North American - Caribbean plate boundary
Describe and give examples of divergent plate boundaries.
Oceanic plates move away from eachother. Convection in the mantle forces magma to rise through the gap between the 2 plates. It spreads, cools and solidifies, adding more sea floor material in a process called sea floor spreading. Divergent boundaries create shield volcanoes, characterised by low viscosity lava, as well as low focal depth, typiocally low magnitude earthuquakes.
Examples include:
Mid-Atlantic Ridge
East-Pacific Rise
Describe and give examples of convergent plate margins
A more dense continental plate, made of basalt, are subducted under less dense continental plate, made of granite. This forms a deep ocean trench. As the oceanic plate enters the mantle, plate material is melted- increasing pressure which is released in the form of a volcanic eruption forming composite volvanoes. Release of tectonic strees at such margins releases energy in the form of an earthquake and may cause uplift of tectonic plates resulting in the water column above it to be displaced, forming a tsunami.
Examples include
Nazca - Pacific plate boundary
North American - Pacific boundary
Describe and give examples of collission plate boundaries
When plates of the same density (both continental or both oceanic) collide, neither can be subducted and are instead forced upwards, forming fold mountains and releasing lots of energy in the form of high magnitude earthuqkaes.
Examples include:
The Himalayas
The Andes
What is slab pull?
Occurs at convergent margins when the oceanic plate is subducetd under the continental plate and pulled into the magma.
What is sea floor spreading?
Occurs at divergent plate boundaries where convection forces magma in the mantle upwards through the crust. The lava cools and solidifies. This adds more sea bed material and forming ridges and shield volcanoes.
What is paleomagentism and why is it useful?
The iron inside magma alligns with Earth’s current magnetic field. When the lava solidifies, the iron is fixed in its orrientation. This emans when the
