Hazards and Processes June 2024 Exam
Questions And Answers
Mantle - Answer>>A layer of rock that due to high temperatures
is deformable (plastic) and flows very slowly
Mantle Plumes - Answer>>Concentrated areas of heat
convection. At plate boundaries they are sheet like, whereas at
hotspots they are columns
Subduction - Answer>>Process of one plate sinking beneath
another at a convergent (destructive) plate boundary
Focus - Answer>>Exact point where an earthquake origionates
Epicentre - Answer>>Point on the earth's surface directly above
the focus
Global Distribution of Tectonic Hazards - Answer>>Mostly
around plate boundaries. I.e. Japan. True for both volcanoes and
EQs.
Factors Affecting Boundary Type - Answer>>1. Motion, whether
plates are moving apart (divergent/constructive), colliding
(convergent/destructive) or sliding past each other
(conservative/transform
2. Plate Type, whether they are Oceanic or Continental
Oceanic Crust - Answer>>Make up the ocean floor, high density
basaltic rock. 7-10 km thick.
Continental Crust - Answer>>Make up the earth's landmasses
and are 25-70km thick. Less dense granite rock.
, Intra-plate events - Answer>>Events/hazards distant from the
plate boundaries at locations called mid plate hotspots I.e. Hawaii
Formation of Island Chains - Answer>>-Isolated Plumes of
convecting heat (mantle plumes) rise to the surface generating
basaltic volcanoes.
-A mantle plume is stationary but the plate above moves slowly
over it.
-This produces a chain of volcanic islands, the extict volcanoes
are further from the plume itself.
Earth's Internal Heat Engine - Answer>>Radioactive decay in
the core and mantle generates heat that causes flow towards the
earth's surface. These heat flows are called convection currents.
Divergent/Constructive (Oceanic-Oceanic) - Answer>>I.e. Mid
Atlantic Ridge, Iceland. Rising convection currents bring magma
to the surface, leading to small basaltic eruptions creating new
oceanic plate. Minor, shallow EQs.
Divergent/Constructive (Continental-Continental) - Answer>>I.e.
African Rift Valleys. Geologically recent mantle plume splits a
continental plate to create a new ocean basin. Basaltic volcanoes
and minor EQs.
Convergent/Destructive (Continental-Continental) -
Answer>>I.e. Himalayas. Collision of of 2 continental
landmasses, creating a mountain range as they both crumple.
Infrequent major EQs.
Convergent/Destructive (Oceanic-Oceanic) - Answer>>I.e.
Alaska. One oceanic plate is subducted beneath another,
generating frequent EQs and an arc of volcanic islands