Reviewer in Earth Science
Exogenic Process or Denudation
The process which occurs on the earth’s surface
due to the influence of exogenic forces.
1. Weathering – action of elements of
weather and climate over earth material.
2. Mass movements – these movements
transfer the mass of rock debris down
the slope under the direct influence of
gravity.
3. Erosion – erosion is the transportation of
rock debris by water, wind, waves, etc.
4. Deposition – is just the end result of
erosion.
Endogenic Process
Is a geological process that was formed,
originated, and located below the surface of the
earth. It involves geologic activities such as
tectonic movements, metamorphism, seismic
activities, and magmatism.
Module 1:
Weathering is the process of breakdown of
rocks at the Earth’s surface. Agents of
weathering are water, salt, temperature, plants,
and animals.
Types of Weathering
1. Physical - is caused by the effects of
changing temperatures on rocks with
sometime assistance of water, causing
the rock to break apart. It happens
especially in places where there is little
soil and few plants grow, such as in
mountain regions and hot deserts. And
there are 3 types of physical weathering:
Abrasion - It occurs when rocks surface is
frequently exposed to water, wind and gravity.
Freeze-thaw - It occurs when water continually
seeps into cracks, freezes and expands,
eventually breaking the rock apart. It occurs in
mountainous regions like the Alps or
Snowdonia.
Exfoliation - It can happen as cracks develop
parallel to the land surface as a consequence of
the reduction in pressure during uplift and
erosion. It occurs typically in upland areas.
2. Chemical weathering – is caused by
rainwater reacting with the mineral
grains in rocks to form new minerals
(clays) and soluble salts. And there are
different types of chemical weathering:
Carbonation – carbon dioxide in the air dissolves
in rainwater and becomes weakly acidic.
Hydrolysis – the breakdown of rock by acidic
water to produce clay and soluble salts.
Hydration – a type of chemical weathering
where water reacts chemically with the rocks,
modifying its chemical structure.
Oxidation – the breakdown of rock by oxygen
and water, often giving iron- rich rocks a rustycolored weathered surface.
3. Biological weathering of rocks occurs
when rocks are weakened by different
biological agents like plants and
animals. It can be classified into:
“” by Physical Means - Burrowing animals like
shrews, moles and earthworms create holes on
the ground by excavation and move the rock
fragments to the surface.
“” by Chemical Compounds - Some plants and
animals also produced acidic substances that
react with the rock and cause its slow
disintegration.
Module 2: Earth’s Internal Heat Sources
Earth was formed about 4.6 billion years ago
and continue to serve as habitat to diverse
organisms. This internal heat comes from the
following sources.
1.
Primordial heat of the planet remains
from its early stage - formed from the
earliest stage of planet Earth which is
molten in state and heat is trapped in
the core of the planet.
2. Heat from the decay of radioactive
elements – This process is known as
radioactive decay by which the
spontaneous breakdown of an atomic
nucleus causes the release of energy
and matter from the nucleus.
3. Gravitational pressure
4. Dense core material in the center of the
planet
Module 3: Endogenic Processes
Partial Melting – when only some parts of a
rock melt.
Decompression melting – takes place within
Earth when a body of rock is held at
approximately the same temperature but the
pressure is reduced.
Factors that affect magma formation:
-
-
Temperature - the higher the
temperature, the higher the
metamorphism grade
Pressure. - like temperature, it changes
the composition, mineralogy, and
texture of rocks. There are two types of
pressures:
a. The vertical stress or confining
pressure- this type of pressure is the
same in all directions and makes the
rocks to fracture or deform.
-
b. The directed or differential pressure
is imposed by a force in a particular
direction. Differential pressure is
dominant at convergent boundaries
Water content (Decreases melting point)
Mineral composition (Different mineral,
different melting point)
Hydrothermal fluids
The rate at which temperature increases
with depth in the Earth’s crust is known as
geothermal gradient.
Foliation is a set of flat or wavy parallel
cleavage planes produced by deformation
under directed pressures.
Metasomatism - in which the alteration
process is caused by fluids passing through
the rock and catalyzing chemical reactions.
Metamorphism is the change of mineral or
geologic texture (distinct arrangement of
minerals) in pre-existing rocks (Protoliths),
without the protolith melting into liquid
magma (a solid-state change).
Types of metamorphism:
Contact metamorphism – results from
temperature increases when a body of
magma contacts a cooler existing rock.
Regional metamorphism – occurs when
great masses of rock change over a wide
area due to pressure.
Dynamic metamorphism – is the result of
very high shear stress, such as occurs along
fault zones. It occurs at relatively low
temperatures compared to other types of
metamorphism.
Burial Metamorphism occurs at lower
temperature and pressure which
transforms sedimentary rocks that had
undergone diagenesis into low-grade
metamorphic rocks through relatively low
temperature and pressure.
Shock metamorphism - takes place when
the heat and shock waves from meteor or
asteroid impact transform rocks immediately
around the impact site.
Plutonism - refers to all sorts of igneous
geological activities taking place below the
Earth's surface. Magma infiltrates the
Earth's crust but fails to make it to the
surface.
Volcanism is used to describe all geological
phenomena that occurs on the natural
terrestrial surface, such as the creation of
volcanoes and hot springs. This motion
takes place inside the cracks that are known
among geologists as natural pipes that
infiltrate the upper mantle.
Module 5: Rock’s behavior under stress
1. Tensional stress causes rocks to be
pulled apart that result to lengthening and
break apart. This type of stress can be found
at divergent plate boundaries.
2. Compressional stress causes rocks to
fold or fracture. It squeezes rocks together.
Compression is the most common type of
stress in convergent plate boundaries.
3. Shear stress happens when forces slide
pass each other in opposite direction which
results to slippage and translation. This is
the most common stress found in transform
plate boundaries.
Geological structures
Folds – are formed when rocks experienced
compressive stress and
deformed plastically.
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A monocline is a simple bend in the
rock layers.
An anticline is a fold that arches
upward where the oldest rocks are
found at the center of an anticline.
A syncline is a fold that bends
downward which rocks are curved
down to a center.
Faults – A rock under ample stress can crack, or
fracture. The fracture is called a joint because
there is a block of rock left standing on either
side of a fracture line. The footwall is the rock
that place on top the fault, while the hanging wall
is below the fault.
Normal faults– divergent boundaries; hanging
wall drops down; East African Rift
Reverse faults –convergent boundaries; hanging
wall moves up; Himalayas Mountains and Rocky
Mountains.
Strike-slip faults – transform plate boundaries;
walls move sideways. It can be either right
lateral or left lateral; San Andreas Fault.
Sea Floor Spreading
The process by which molten material adds new
oceanic crust to the ocean floor
Mid-Ocean Ridge: The undersea mountain chain
where new ocean floor is produced; a divergent
plate boundary
Sonar: A device that determines the distance of
an object under water by recording echoes of
sound waves
In the 1960s, Harry Hess proposed that the
ocean floors move like conveyor belts, carrying
the continents with them.
Evidences for seafloor spreading
Evidence from molten material - Alvin’s crew
found strange rocks shaped like pillows or like
toothpaste squeezed from a tube
Evidence from magnetic stripes - Scientists
discovered that the rock that makes up the
ocean floor lies in a pattern of magnetized
“stripes”
Evidence from drilling samples - When scientists
sampled the rocks, they found that the further
away from the ridge the rocks were the older
they were
Deep-ocean trenches - A deep valley along the
ocean floor through which oceanic crust slowly
sinks towards the mantle
Subduction: The process by which oceanic crust
sinks through a deep-ocean trench and back
into the mantle; a convergent plate boundary
Subduction in the Pacific Ocean is occurring at a
greater rate than sea-floor is expanding. This is
caused by the large number of trenches.
The Atlantic Ocean is expanding at a greater
rate than subducting. This is because of the low
number of trenches in the Atlantic.
Continental Drift
Alfred Wegener found evidence for Pangaea
and proposed the area of continental drift.
Theory that continents were once part of a
single landmass that broke apart and have
moved to their present locations.
Wegener’s evidence
-
Continents “fit together” like puzzle
pieces
Mid-Ocean Ridge: The undersea
mountain chain where new ocean floor
is produced; a divergent plate boundary
-
Some mountain ranges on different
continents seem to match
Climatic evidence such as glaciers in
areas that are close to equator
(LAGEOS) Laser Geodynamics Satellite
is used to measure the movements of
continents
Theory of Plate Tectonics
The theory that pieces of Earth’s lithosphere
are in constant motion, driven by convection
currents in the mantle.
7. Trench- It is the deepest part of the
ocean.
8. Mid-oceanic ridge- The seafloor mountain
system which is situated in the middle of the
ocean basin. It is where upwelling of magma
happens which causes the sea floor to
spread.
Wilson’s Cycle
Stage
Embryonic
Module 7: Structure and Evolution of ocean
basins
1. Continental shelf- Partly shallow
extension of the continent underwater.
Juvenile
2. Continental slope- Transition zone of
continental shelf and deep ocean floor. It
starts from oceanic crust to continental
crust.
3. Continental rise- It is where the ocean
begins. All basaltic and oceanic rocks are
found here. It is the place where the
sediments from land are washed. The
continental margin starts from continental
shelf up to continental rise.
4. Abyssal plain- The flattest part of the
ocean. 50 % of the earth’s surface is being
covered by this plain.
Mature
Declining
5. Island- It’s not just a piece of land floating
up in the middle of the sea, it is part of the
ocean basin that extends up from the ocean
floor.
6. Seamount- It is an undersea mountain.
The erosion caused by waves destroyed the
top of a seamount which caused it to be
flattened.
Terminal
Description
Motion: Uplift
Complex
system of
linear rift
valleys on
continent
Motion:
Divergence
(spreading)
Narrow seas
with
matching
coasts
Motion:
Divergence
(spreading)
Ocean basin
with
continental
margins
Example
East African
Rift Valleys
Motion:
Convergence
(Collision and
Uplift)
Islands arcs
and trenches
around basin
edge
Motion:
Convergent
(Collision and
Uplift)
Narrow,
irregular seas
Pacific Ocean
Red Sea
Atlantic and
Arctic oceans
Mediterranean
Sea
Suturing
with young
mountains
Motion:
Convergence
and Uplift
Young to
mature
mountain
belts
Himalayas
Mountains