Lecture #1 & 2 The Dynamic Earth
Lecture #1 & 2 The Dynamic Earth
Lecture #1 & 2 The Dynamic Earth
Development
QAB 4053 (Bachelor, Petroleum Geoscience)
Lectures # 1 & 2
The Earth, A Dynamic Planet
January 2013
Assoc. Prof. Dr Abdelaziz Lotfy Abdeldayem
Department of Petroleum Geosciences
Learning Outcomes
By the end of this lecture students should
be able to:
Understand the global structure of the Earth.
Realize the surface expression of the internal
dynamics of Earth.
Visualize the interaction of different plate
boundaries in relation to Earth dynamics.
QAB 4053 Geodynamics & Basin Development
Introduction
The Earth is a dynamic planet with surface constantly
changing by internal and external processes resulting in
EARTHS INTERIOR
Seismic discontinuities aid
in distinguishing divisions
of the Earths layers into:
inner core,
outer core,
D (Gutenberg)
lower mantle,
transition region,
upper mantle,
Mohorovicic, and
crust (oceanic &
continental).
Lateral discontinuities
have also been
distinguished and mapped
through seismic
tomography.
http://www.solarviews.com/eng/earthint.htm
QAB 4053 Geodynamics & Basin Development
http://www.geoexpro.com/article/Mid_Cretaceous_Source_Rock_Enigma/cb946b8a.aspx
STRUCTURE OF EARTH
Tectonics
In geologic terms, the word tectonics, in a broad
sense, includes the study of Earths structures on
every scale. In a narrower scale, it deals specifically
with very big structures like oceanic ridges, geosynclines, and mountain belts and in the same
sense it is sometimes called Geotectonics to
emphasize its global aspect.
Tectonics, therefore, concerns with the major relief
features of the Earths surface and the attempt to
bind them into a cohesive pattern/ model.
QAB 4053 Geodynamics & Basin Development
Tectonics
In other words, tectonics deals with the
structures within the lithosphere of the
Earth, including those related to orogenies
and tectonic development of cratons and
terranes as well as the earthquake and
volcanic belts, particularly with the forces
(compressional
and
tensional)
and
movements that have operated to create
these large structures.
QAB 4053 Geodynamics & Basin Development
http://www.see.leeds.ac.uk/structure/dynamicearth/history/index.htm
What is Geodynamics?
It is a subfield of geophysics that studies the
processes leading to deformation of Earths mantle
and crust and the related earthquakes and volcanism
that shape its structure.
It deals with the processes that govern the large
scale structure of Earth, i.e., those that act on the
scale of the whole lithosphere.
Geodynamic processes have operated throughout
the Earth's history to create, destroy and recreate
continents & oceans, geological provinces & terranes,
mountain chains and basins.
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QAB 4053 Geodynamics & Basin Development
What is Geodynamics?
It discusses how mantle convection leads to plate
tectonics and geologic phenomena such continental
drift, seafloor spreading, mountain building, formation &
development of sedimentary basins and so on.
http://cct.gfy.ku.dk/publ_cct/cct1721.htm
Viscous behavior: is suitable for modeling sublithospheric mantle/ magma flow. Almost all geological
materials behave viscous on a long-time scale.
An Example of Numerical
Geodynamic Modeling
Plate Tectonics
Plate tectonics is based on two concepts that
appeared separately;
Continental Drift
Sea-floor Spreading
I. Continental Drift
Introduced formally in 1912 by German meteorologist
Alfred Wegener who contended that, around 200 million
years ago, there existed a supercontinent, Pangaea,
that began to split apart.
In 1939, it was proposed that Pangaea first broke into
two large continental landmasses, Laurasia in the
northern
hemisphere
and
Gondwanaland
in
the
Continental Drift
A fatal weakness in Wegener's theory was that he could not
satisfactorily answer the most fundamental question raised by
his critics: What kind of forces could be strong enough to move
such large masses of solid rocks over such great distances?
Wegener suggested that the continents simply plowed through
the ocean floor, but this was found to be physically impossible
comprise mountain ranges, deep-sea trenches, midoceanic ridges and major faults. He then postulated that
these mobile belts are not isolated lineations but rather
are all interconnected in a global network. This network
of faults, ridges, and trenches outlines about a dozen
large
plates
and
numerous
smaller
ones,
each
These
plate
boundaries
have
different
names
Earth's lithosphere is presently divided into 16 large plates with about 24 smaller ones
that are drifting above the mantle at the rate of 5 - 10 cm (2 to 4 in) per year
Scotia
Plate
As the figure
shows, tectonic
plates fit together
over the Earth.
they act as a cover
over the Earth's
mantle and core.
The question now:
What are Tectonic
Plates made of and
what drives them?
http://www.freewebs.com/morganisrupert/photos.htm
59
Plate boundaries and velocities and directions of movement. The lengths of the arrows
are proportional to the velocity of plate movement; the numbers represent velocity in
centimeters per year.
Upper plate
- Oceanic
Continental
- Oceanic
Oceanic
- Continental
Continental
Convergent plate margins are marked in two ways: either by deep trenches,
where plates of oceanic lithosphere converge and one descends to be recycled
into the mantle, or by high folded mountain belts. In both cases, earthquakes and
magma (volcanic activities) are generated. Absolute plate motions are shown
with arrows. Trenches and mountain belts are labeled.
Complex folds, mountains, and plateaus mark the collision zone between India
and Eurasia, as shown on this digital shaded relief map. The collision also drove
parts of Southeast Asia and China eastward along lengthy strike-slip faults or
shear zones. (Courtesy of Ken Perry, Chalk Butte, Inc.)
or
destructive
plate
boundaries
move
Section of the San Andreas Fault in the Carrizo Plain, western California.
(U.S. Geological Survey)
QAB 4053 Geodynamics & Basin Development
CONCLUSIONS
The global structure of the inner Earth is layered
according to density as viewed indirectly by seismic.
Plate tectonics is the surface expression of the
Earth internal dynamics.
Plate tectonic boundaries mark locations and
explain recurrence of volcanic and earthquake
activities worldwide.
Plate tectonics is important in developing O & G
accumulations at diverging and converging sites.
QAB 4053 Geodynamics & Basin Development