Transcript Branches of Earth Science

EARTH SCIENCE
Earth Science is the name for all the sciences
that collectively seek to understand Earth and its
neighbours in space.
Aspects that make Earth Science different from other
sciences :
1) it draws from all other sciences (physics, chemistry,
meteorology, astronomy, biology, etc.)
2) it requires consideration of vast amounts of time with
sequencing of events (chronology) and ages.
3) it has a global perspective.
MAJOR BRANCHES OF EARTH
SCIENCE
1) Geology – study of the solid Earth
• Divided into two broad areas;
A) Physical Geology - examines the materials composing
Earth and seeks to understand processes that operate beneath
and upon its surface.
B) Historical Geology – seeks an understanding of the
origin of Earth and the development of the planet through its
4.6 billion year history.
SOLID EARTH
Seismology – study of earthquakes and seismic waves
Paleontology – study of fossils and life on Earth
Geomorphology – study of landscape features on Earth
Mineralology – study of minerals
Volcanology – study of volcanic activity
Crystallography – study of volcanic activity
Petrology – study of volcanic activity
Stratigraphy – study of volcanic activity
Sedimentology – study of volcanic activity
LIQUID EARTH
2) Oceanography
• study of the oceans and oceanic phenomena
• study of the composition and movements of sea water, as .
well as coastal processes, seafloor topography, and marine life
Hydrology
• study of Earth’s fresh water systems
• including, rivers, streams, and groundwater
GASEOUS EARTH
3) Meteorology – study of the atmosphere; weather and
climate
Space
4) Astronomy – study of the universe and the relationship
between Earth and the universe
ORIGIN OF THE UNIVERSE
Historically many ideas about the origin of the
universe has been hypothesized:
Creationism - where some supreme being (God)
created the universe.
The Big Bang - an effort to explain what happened at
the very beginning of our universe based upon
discoveries in astronomy and physics.
THE BIG BANG
Our universe is thought to have begun as an infinitesimally
small, infinitely hot, infinitely dense, something - a
singularity. After its initial appearance, it apparently
inflated, the "Big Bang”.
Raisin Bun Analogy
THE BIG BANG

universe was confined to a dense, hot, super
massive ball of gases

20 billion years ago, an explosion hurled this
material in all directions

marked the origin of all matter and space
THE BIG BANG

gases cooled and condensed forming stellar systems
that we call galaxies
ORIGIN OF SOLAR SYSTEM
Solar Nebular Hypothesis:
Explained the formation
of the solar system
through four stages.
New text pp. 18-20
SOLAR NEBULAR HYPOTHESIS:
 Approximately 5 billion years ago
 Huge mass of dust and gases began to contract under
. its own gravity
 Gas cloud began to rotate faster and faster as it contracted
SOLAR NEBULAR HYPOTHESIS:
 rotation caused most material to concentrate in the center
 the central rotating mass of gases was packing tightly. .
. . upon itself and this caused it to heat up and burst into a
. . newborn sun.
 remaining dust and gases orbited around the central body
. as a flattened disk
SOLAR NEBULAR HYPOTHESIS:
 temperatures within the rotating disk dropped and small
. particles such as iron and nickel started to form
 these particles collided for millions of years and accreted
. to form the planets, moons, and other small bodies
SOLAR NEBULAR HYPOTHESIS:
 as planets accumulated more particles, space in between
. the planets started to clear
 with time, most of the remaining debris was swept into
. space by solar winds
HISTORY OF GEOLOGY

Science is the investigation of ideas. Throughout
history, scientific ideas change as new evidence is
discovered regarding scientific models and theories.

These changing ideas were demonstrated
throughout geologic history. One notable change
that formed the framework for geologist is the
movement from Catastrophic ideas to one of
uniformity, hence the birth of the principle of
Uniformitarianism.
Reference:
New text, pages 5 - 6
EVOLUTION OF SCIENTIFIC KNOWLEDGE
The evolution of scientific knowledge does
not emerge from the straightforward
accumulation of facts, but rather from a set
of changing intellectual circumstances and
possibilities. (Kuhn)
Hypothesis
 a preliminary, untested, educated guess which
provides an explanation to some idea.
Theory
 an hypothesis that has undergone extensive scrutiny and
all competing hypothesis have been eliminated can then
be referred to as a scientific theory.
 explain observable facts which occur in nature. Subject to
change.
Law
 a generalization about the behaviour of nature from
which their has been no known deviation after numerous
observations or experiments.
 Describe observable facts which occur in nature.
Paradigm
 A set of belief or values of a person or society.
ORIGIN OF EARTH
To understand the origin of Earth, we must focus
on how Earth formed ~ 4.5 billions of years ago.
Earth formed as a direct result of the “Solar
Nebula Hypothesis”.
EARLY EARTH
 The Earth was not always layered as it is today.
The Earth was a lot like the moon in appearance
billions of years ago.
 The composition of the ancient Earth was thought to
be the same throughout.
SEGREGATION OF EARTH

Shortly after Earth formed, the interior of
Earth segregated and took on a layered structure.
Heat generated from the collision of particles,
decay of radioactive isotopes and residual heat in
the Earth’s interior was responsible for melting the
heavier elements (Ni and Fe).
SEGREGATION OF EARTH

Gravity caused great streams of hot heavy liquids to
move toward the Earth’s center, melting the lighter
rock material and forced it to the surface.

This sorting of material by density,(differentiation)
early in Earth’s history, is still occurring today, but
on a smaller scale.

Gases were released from Earth’s interior through
volcanoes .
SEGREGATION OF EARTH
Crust
Inner Core
Outer Core
Mantle

The heavier material (nickel and iron) which
concentrated close to Earth’s center formed the inner
and outer core.

The lighter and less dense material which moved
upwards closer to the surface formed Earth’s crust.

The material in between formed earth’s mantle.
SEGREGATION OF EARTH
Atmosphere
Hydrosphere
Geosphere

Atmosphere and oceans formed as a result of the gases
given off by volcanic out gassing throughout Earth’s
history.
ORIGIN OF ATMOSPHERE
(A)
(B)

During the early stages of segregation of Earth (A),
gaseous materials escaped from Earth’s interior,
(a process called outgassing) much the same way as
gases are released from volcanoes today.

An atmosphere gradually evolved, composed mainly of
gases released from within the planet (B). Earth’s
original atmosphere consisted of; water vapor,
carbon dioxide, nitrogen and several trace gases.
ORIGIN OF ATMOSPHERE
(A)

(B)
Earth’s original atmosphere had a different composition than
Earth’s present atmosphere. Note the following comparison:
Original Atmosphere
Present Atmosphere
 mainly water vapor
 mainly nitrogen (79%)
 no free oxygen
 contains free oxygen (20%)
 High percentage of CO2
 less than 1% CO2
EVOLUTION OF THE ATMOSPHERE
If Earth’s atmosphere formed from volcanic outgassing
(no free oxygen), where did the high percentage of
oxygen (20%) in the present atmosphere come from?
 The main source of oxygen is from green plants. Plants carry out
photosynthesis where they consume carbon dioxide and release
oxygen.
 In time the oxygen reached the atmosphere and accumulated to
its present day percentages.
EARTH’S INTERIOR
The model is based on
indirect evidence from
the study of seismic
waves. The diagram to
the left outlines the four
major layers inside of
Earth.
LAYERS OF EARTH’S INTERIOR
Lithosphere
Lithosphere
 cool, rigid layer located directly above the asthenosphere.
 approximately 100 km thick, which includes the entire
crust and a portion of the uppermost mantle.
 comprise the tectonic plates (sometimes called
lithospheric plates).
LAYERS OF EARTH’S INTERIOR
Crust
Crust (two types)
1) Continental Crust
– 30 to 40 km thick and has low density. ( sialic rock )
2) Oceanic Crust
– approximately 5 km thick and has high density. (simatic
rock )
LAYERS OF EARTH’S INTERIOR
Moho
Mohorovicic Discontinuity (Moho)
 boundary separating the crust and the mantle.
 distinguished by an increase in rock density.
 velocity of seismic waves show an increase.
LAYERS OF EARTH’S INTERIOR
Asthenosphere
Asthenosphere (Upper Mantle)
 located approximately 100 km to 700 km in depth.
 hot, weak zone of rock that is capable of gradual movement.
(semi-liquid, plastic like )
 This is the layer that the crustal plates rest upon.
LAYERS OF EARTH’S INTERIOR
Lower Mantle
Lower Mantle
 this layer is approximately 2200 km thick.
 consist of high density rocks rich in compounds of iron,
magnesium, and silicon.
LAYERS OF EARTH’S INTERIOR
Outer Core
Outer Core
 approximately 2270 km thick.
 consist of liquid iron and nickel.
 seismic waves (S-waves) do not pass through this layer.
LAYERS OF EARTH’S INTERIOR
Inner Core
Inner Core
 approximately 1216 km thick.
 consist of solid iron and nickel.
TEMPERATURE AND DENSITY
INCREASES WITH DEPTH

Temperature inside Earth increases at a rate of
approximately 35 degrees celcius per kilometer.
This is referred to as the Geothermal Gradient.
TEMPERATURE AND DENSITY
INCREASES WITH DEPTH

Density inside Earth increases as depth
inside Earth increases.
EARTH’S SPHERES
 The Earth is a system
of four interdependent
reservoirs through which
matter and energy flows.
These four reservoirs are;
1) Geosphere,
2) Hydrosphere,
3) Atmosphere, and,
4) Biosphere.
These spheres function
as one system.
GEOSPHERE

The entire solid Earth from the core to the surface.

Examples that we see include the continental and
oceanic crust.
Hydrosphere

All of the waters of the earth, including both surface
and subsurface waters including ice.

Examples include oceans, glaciers, lakes, rivers, and
ground water.
ATMOSPHERE

The gaseous layer which surrounds Earth, mainly
comprised of nitrogen, oxygen and carbon dioxide.

Examples include the air we breath.
Biosphere

The layer of life existing throughout the three
preceding spheres.

Examples include plants, animals, birds and fish.
The spheres formed in the following order:
geosphere; hydrosphere, atmosphere, biosphere.
EARTH’S SPHERES
 The parts of the Earth System are closely linked so that a
change in one part can produce changes in any or all of the
other parts.
 Example:
Volcanic eruptions;
- can interfere with surface drainage.
- can interfere with incoming solar radiation. Thus,
change weather and climate (short term and long term).
- can interfere with the biosphere. Sensitive life-forms
may be eliminated.
EARTH’S SPHERES
 Earth System is powered by two sources;
1)
Sun (solar energy) drives external processes of Earth.
For example, weather and climate, ocean circulation,
and erosional processes.
2)
Residual heat and Radioactivity drives internal
processes of Earth. For example, volcanoes,
earthquakes and mountain building.