Earth Systems 3209 – Study Guide – Emily V. Walsh

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PART 3: FORMATION OF EARTH AND THE UNIVERSE

1. Origin of the Universe: there are many theories on the origin of the universe.

Paradigm: a widely accepted idea in science. A paradigm shift is a sudden change in the popular opinion (ex. The paradigm of the world being flat shifted to the paradigm that the world is a sphere).

Catastrophism/Creationism: catastrophism is the belief that every part of Earth was created in a massive catastrophic event (ex. The Grand Canyon being created in a single flood). This directly relates to creationism, which is the belief that a high power (ex. God) directed these catastrophes and created all life on Earth. These beliefs allow for Earth’s timeline to be about 6000 years old, which corresponds with the Christian Bible.

Uniformitarianism: the belief that any process that occurs on Earth today has always occurred, and that these occurrences are what created the universe and everything in it (ex. Erosion happens today, therefore it has always happened, therefore we can state that the Grand Canyon was formed over a very long period of time from erosion). This belief allows for Earth’s timeline to be about 4.6 billion years old.

o The Big Bang Theory: the theory that the universe originated sometime between 10 billion and 20 billion years ago from the cataclysmic explosion of a small volume of matter at extremely high density and temperature.

o (Solar) Nebula Hypothesis: theory of the formation of the planets that states that a rotating nebula contracted and was then torn into fragments by centrifugal forces, with planets condensing from the fragments. The steps of the Solar Nebula Hypothesis are:

1. A nebula (huge mass of dust and gas) forms about 5 billion years ago.

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2. It begins to contract and spin under its own gravity.

3. Material begins to concentrate, packing into an extremely small volume.

4. The concentration bursts, creating the sun and pushing the remaining dust into the new galaxy.

5. The remaining dust begins to collide and accrete, forming planets, moons and other solid bodies.

6. Remaining dust is pulled to these bodies by their gravities.

7. Individual planets and moons begin to reform themselves into their current state.

o Segregation/Differentiation: the separation of elements on a planet based on density. It is believed that, as the core of a planet heats up, that this occurs in all planets, allowing heavier elements to sink to the core with gravity, and lighter elements to remain at the surface. This creates layers within planets. There are three hypothesized sources of heat for new planets:

i. Radioactive (Nuclear) Decay: the process by which an unstable atomic nucleus loses energy by emitting ionizing particles or radiation. The emission is spontaneous in that the nucleus decays without collision with another particle. This process releases heat energy.

ii. Meteorites: the impact of large meteorites would create heat through friction.

iii. Gravitational Contraction: the force of gravity releases heat.

2. Spheres of Earth: Earth itself contains four main spheres of existence.

Atmosphere: everything that makes up the air, weather, etc.

Geosphere/Lithosphere: everything that makes up solid Earth and liquid rock.

Hydrosphere: all water on Earth.

Biosphere: all living things on Earth. o Photosynthesis: a process by

which green plants and other organisms turn carbon dioxide and water into carbohydrates and oxygen, using light energy trapped by chlorophyll.

o Ecological Succession: the series of changes that create plant and animal communities (ecosystems). For example, a rocky area

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with no life may first be colonized with bacteria. Next mosses, then rodents etc. Until a full ecosystem is developed.

3. Formation of the Earth: with studies of uniformitarianism, we can understand the

theory on how the Earth was formed.

Formation of the Geosphere o Earth Layers: the following are the current layers of the Earth, as were

established by segregation. - Inner Core: The inner core of the Earth, its innermost hottest part

as detected by seismological studies, is a primarily solid sphere about in radius, only about 70% that of the Moon. It is believed to consist of an iron-nickel alloy, and may have a temperature similar to the Sun's surface. (From 5150 km deep to 6380 km deep)

- Outer Core: The outer core of the Earth is a liquid layer about 2,260 kilometers thick composed of iron and nickel which lies above the Earth's solid inner core and below its mantle. (From 2900 km deep to 5150 km deep)

- Mantle/Athenosphere: region of the earth's interior between the crust and the core, believed to consist of hot, dense silicate rocks.

i. Lower Mantel: the deeper portion of the mantle. (From 250 km deep to 2900 km deep)

ii. Upper Mantle: the higher portion of the mantle. (From 100 km deep to 250 km deep)

Mohorovicic Discontinuity (Moho): the boundary between the Earth's crust and the underlying mantle.

- Lithosphere: the solid part of the earth consisting of the crust and outer mantle. (From the surface to about 100 km deep)

i. Crust: the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle.

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o Precambrian Shields: a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas. Similar to tectonic plates, except that they don’t move around.

- Canadian Shield: the Precambrian shield that is under most of Canada, part of the United states, and part of Greenland.

o Continent: large connected mass of land that makes up all dry land on Earth, usually separated by massive bodies of water, like oceans.

- Modern Day Continents: today, there are seven continents. 1. Asia 2. Antarctica 3. South America 4. North America

5. Europe 6. Oceania 7. Africa

- Super-continents: over billions of years, continents have shifted, creating the following super-continents (meaning massive continents). These continents may have contained two or more of the modern day continents, the most important one begin Pangea because it contained every single modern day continent.

1. Pangea 2. Gondwana 3. Laurasia

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Formation of the Atmosphere o The Precambrian Atmosphere: our early atmosphere first consisted of

hydrogen and helium which, because of their very small masses, easily escaped into space if they did not combine with another element. A little later in the Precambrian, it’s believed that methane and ammonia formed as a result of volcanic outgassing.

- Volcanic Activity/Outgassing: aside from lava, volcanoes release water vapor, carbon dioxide, carbon monoxide and nitrogen into the air. It is believed that volcanoes were the original source of these atmospheric substances and that some, but not all, of it reacted to form methane and ammonia.

o Oxygen Production: oxygen appeared in the atmosphere much later in the Precambrian eon. It’s believed that tiny organisms that did not need oxygen to survive, but who produced oxygen as a by-product were the cause of the sudden formation of oxygen.

- Cyanobacteria: tiny bacteria that live off of chlorophyll. They use various gases to survive and produce oxygen as a by-product. These bacteria still live today in extreme environments.

i. Stromatolites: a large mound of Cyanobacteria. - Evidence: there is a lot of evidence supporting this theory of the

origin of oxygen on Earth. i. Fossils: tiny fossils of Cyanobacteria that dates back to the

Precambrian Eon have been found. ii. Banded Iron Formations: rocks that contain small

amounts of rust. Because iron reacts with free oxygen to form rust, we can assume that there was some free oxygen in the water at this time.

iii. Red Beds: rocks from about 1.8 million years ago to the present that contain rusted iron deposits. This is strong evidence of free oxygen in the air from that time period.

Formation of the Hydrosphere o Water Vapor: volcanoes release water vapor as they explode. o Extraterrestrial Origin: some extraterrestrial bodies, such as comets, are

made of or contain some ice, which can melt to water if it strikes the Earth.

Formation of the Biosphere o Origin of Life on Earth: in order for life to have originated on Earth, the

basic building blocks of organisms must have been created under certain circumstances. The building blocks needed are: Proteins, Nucleic Acids (RNA & DNA), Carbohydrates, and Lipids (Fats) (for this course, we only need to know the following about Proteins and Nucleic Acids).

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- Original Protein Formation: it has been proven that, under the conditions of the Precambrian Atmosphere, the first proteins could be formed. Because proteins are the building blocks of living things, this could have been the origin of the first living species.

i. The Urey-Miller Model: Urey and Miller were the scientists who finally proved that theory. They filled an atmospheric chamber with carbon dioxide, nitrogen, water vapor, methane, and ammonia and exposed it to sparks (mimicking lightening). Sure enough, amino acids (tiny pieces of proteins) were formed.

- Role of Nucleic Acids: nucleic acids are like instructions for proteins on how to build a living thing.

i. RNA: single stranded nucleic acid that carries instructions from DNA to proteins.

ii. DNA: double stranded nucleic acid that holds the instructions for the RNA to take.

iii. Their Role: It’s believed that RNA existed in Precambrian Earth, and DNA developed later. Extremely simple organisms contain RNA only, so the first life on Earth may have been RNA based.

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o Continued Development of Life: after DNA, RNA and proteins were formed, they could come together with other macromolecules to form the first life on Earth.

- Prokaryote: a one-celled simple organism - Eukaryote: a well structured organisms, usually multicellular.

Eukaryotes subdivide into plants and animals. - Varangian Glaciation: an ice age, one of the biggest in history,

that wiped about most of Earth’s species at the time. - Ediacara Fauna: some of the most well-preserved soft-bodied

fossils of organisms of all time, found in Australia and dating back to the Late Proterozoic Era.