Download (comprised of the continental crust and oceanic crust).

The Structure of the Earth
The planet Earth is
comprised of a number of
concentric layers. At the
center is the core (a solid
inner core and a liquid
outer core). Surrounding
the core is the mantle
(similar to mafic minerals
like olivine and the
ultramafic peridotite). The
outer most layer is the
crust (comprised of the
continental crust and
oceanic crust).
The Lithosphere
Geologists use the term lithosphere to mean an outer Earth
zone, or shell, of rigid, brittle rock. It includes not only the
crust, but also the cooler, upper part of the mantle that is
composed of brittle rock.
The rigid, brittle lithosphere rests on top of a soft, plastic
underlayer named the asthenosphere.
The lithospheric shell consists of large pieces called
lithospheric plates.
The Lithosphere
(a) Idealized cross section of the Earth's crust and
upper mantle. (b) Details of the crust and mantle at
the edge of a continent, including the types of rocks
found there. Also shown are the lithosphere and
asthenosphere.
Continents and
Ocean Basins
The major relief features of the Earth are the
continents and ocean basins.The continental masses
consist of two basic subdivisions: (1) active belts of
mountain-making and (2) inactive regions of old,
stable rock.
Continents and Ocean Basins
Principal mountain arcs, island arcs, and trenches of
the world and the mid-oceanic ridge.
The Ocean Basin
A typical ocean basin is characterized by a central ridge structure that
divides the basin in about half. The midoceanic ridge consists of
submarine hills that rise gradually to a rugged central zone.
The continental margins are narrow zones which separate ocean crust
from continental crust. From the ocean to the land it is comprised of the
continental rise, then the continental slope, then the continental shelf.
The Ocean Basin
This block diagram
shows an inner wedge
of sediments beneath
the continental shelf
and an outer wedge of
deep-sea sediments
beneath the continental
rise and abyssal plain.
This schematic block diagram
shows the main features of ocean
basins. It applies particularly well
to the North and South Atlantic
oceans.
Plate Tectonics
The study of the motion of lithospheric plates and their
interactions at their boundaries is plate tectonics. Tectonics
refers to the breaking and bending of the entire lithosphere,
including the crust.
*See movie on plate tectonics in the geodiscoveries section of your text’s
website.
Plate Tectonics
Diagram (a) is greatly exaggerated in vertical scale, and emphasizes
surface and crustal features. Diagram (b) is drawn to true scale. Here the
actual relationships between lithospheric plates can be examined, but
surface features are too small to be shown.
The Lithospheric
Plates
The rigid outer lithosphere is
divided into a number of
lithospheric plates of various
shapes and sizes. The boundaries
also differ according to whether
plates are coming together
(converging), moving apart
(spreading) or moving alongside
each other (transform).
To explore the lithospheric plates
further, visit the Animated Globe
by clicking the globe icon on the
menu bar. To return to this
presentation, click "Previous".
Tectonic Plate Boundary
Relationships
There are three major kinds of active plate boundaries:
1.
Spreading boundaries - New lithosphere is being formed by accretion.
2.
Converging boundaries - Subduction is in progress, and lithosphere is
being consumed.
3.
Transform boundaries - Plates are gliding past one another on a
transform fault.
*See movie on tectonic plate boundary relationships in the geodiscoveries section of your
text’s website.
Continents of the Past
The distribution of continents was very different in the past than it is
today. A single supercontinent, named Pangea, existed around 250
million years ago. It split up over time, and as the continents drifted we
arrived at today’s pattern of land and sea.
*See animation on continental drift/change in the geodiscoveries section of your text’s
website.