identify each part of the earth’s structure from a diagram; zzdescribe the key elements of each part of the earth’s structure; zzname and locate all of the earth’s main plates;
zzexplain Alfred Wegener’s theory of continental drift and its proofs; zzexplain Harry Hess’s theory of sea-floor spreading and its proofs; describe the theory of plate tectonics;
zz zzdescribe the processes at work at each plate boundary and their impacts on the landscape. Syllabus Link: 1.1, 1.2, 1.3
KEYWORDS earth
continental crust oceanic crust Moho
mantle lithosphere asthenosphere
convection currents
outer core inner core
continental drift Pangaea
tectonic plate mesosaurus sea-floor spreading magma
The Earth’s Structure
The crust is the earth’s outer layer. It has two zones, each made of solid rock (Fig. 1.1(a)). zz
Continental crust comprises the continents and continental shelves, covering approximately 40% of the earth’s surface. Its older, lighter rocks (e.g. granite) contain high quantities of two minerals – silica and alumina (SIAL). It varies in thickness from 25 km to 70 km.
zz
Oceanic crust covers 60% of the earth’s surface. Its heavier, denser rocks (e.g. basalt) contain high quantities of silica and magnesium (SIMA). It varies in thickness from 3 km to 10 km.
A-Z
Endogenic forces: Forces within the earth’s crust which cause the earth’s surface to move horizontally and vertically.
Moho Lithosphere Solid upper mantle Asthenosphere
Oceanic crust Continental crust
The Moho is a boundary found in the lithosphere which divides the upper mantle and the crust. It was named after Andrija Mohorovicic (1857–1936), the seismologist who discovered the feature.
Fig. 1.1(a) The lithosphere and asthenosphere. 1
