Summary Hazardous Earth-Complete A* Case Study & Theory Notes (OCR A-Level)

Hazardous
Earth

, Oceanic crust : 5-10 km thick
,
basaltic
,
dense 3glam
Continental cust : 30-70 km thich
, granitic ,
less dense 2
Tglan
.




Tectonic theory
:



1 .
Weghner-Pangea , fossil +
geological fit accross continents
.
2 Hess sea floor mid
spreading + ocean
ridges
-




.
3 Paleomagnetism - Reversed magnetic strips -
Show Oceanic crust
formation




Plate Boundaries

constructive -


plates more apart
to
magna + fill gap
-




Basaltic low lava Shield volcanoes
viscocity
-
>
-
,

-


Shallow earthquakes ↳ effusive


Destructive :


·
Oceanic-continental

denser plate subducts under continental
-



oceanic

·
Oceanic -
oceanic
-
older
plate Subducts
Continental
· -
Continental
-


plates crumple to form mountains
=


Explosive volcanoes
(andesitic/rhyolitic
Conservative -


plates slide past
no volcanoes
generation
>
no
magna
- -




-


high friction >
-
shallow+ powerful earthquakes
↳ stress release