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 Hydrology 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 Raisin Bun Analogy 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

Solar Nebular Hypothesis: 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 The heavier material (nickel and iron) which concentrated close to Earth’s center formed the inner and outer core. Inner Core Outer Core The lighter and less dense material which moved upwards closer to the surface formed Earth’s crust. Crust The material in between formed earth’s mantle. 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) Continental Crust – 30 to 40 km thick and has low density. ( sialic rock ) 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.

Hydrosphere Geosphere The entire solid Earth from the core to the surface. Examples that we see include the continental and oceanic crust. All of the waters of the earth, including both surface and subsurface waters including ice. Examples include oceans, glaciers, lakes, rivers, and ground water. Hydrosphere

Atmosphere The gaseous layer which surrounds Earth, mainly comprised of nitrogen, oxygen and carbon dioxide. Examples include the air we breath. The layer of life existing throughout the three preceding spheres. Examples include plants, animals, birds and fish. Biosphere 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.