Historical Geology Test 1 Study Guide

Big Bang Theory

• What is the Big Bang and describe the explosion? It is the Time and space set a zero in minuscule volume, meaning, the universe was all in one place. All its matter and energy were squished into an infinitely small point, a singularity, and then it exploded! The universe began about 14.4 billion years ago. The explosion happened 3-20 minutes after the Big Bang.

• Evidence that supports the Big Bang theory: Doppler effect with sound waves (Pitch changes when an object moves closer), Bright Line Spectra (Infrared lights and visible light, when a galaxy is shifting closer, light will shift blue on the spectrum, and when a galaxy is moving away, light will shift red on the spectrum), and Hubble’s Law (1929, Edwin Hubble found evidence to support Lamitre’s theory.

Solar Nebular Theory

• What is a Nebula? The birthplace of our Solar System is a cloud of gas and dust within the universe.

• Be able to describe the history of our Solar System: Gravity caused the gases and dust to be drawn together into a denser

  cloud (rate of rotation increased), The cloud collapsed to resemble a disk, Protoplanets formed (mini planets), and Hydrogen/ helium atoms (nuclear fusion)

• Suns Formation, including Nuclear fusion: Enormous pressure and heat

  cause hydrogen to combine into helium atoms, light energy in the core

• Age of Earth, Moon, and Oldest Rock: Earth is approximately 4.56 billion years old, the Moon formed approximately 4.5 billion years old (Right after the Earth), and the oldest rock is 4.47 billion years old.

• Evidence to support Solar Nebular Theory: The position of our planets, hydrogen and helium elements, and the Sun, moon, and oldest rock forming around the same time.

Early Earth

• How do elements arrange themselves? They arrange themselves according to density. (Least dense make up the atmosphere, most dense make up the core)

• Earth's early atmosphere: Earth’s early atmosphere probably contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water (All are toxic gases

  except H20.)

• When did the first oceans form and how? They formed 3.8 billion years ago and the Earth was cool enough to have liquid water.

• The first cells are thought to have originated 200-300 million years after oceans formed.The presence of liquid water was necessary for first life. Earliest cells called proteinoid microspheres were created when organic molecules became trapped in bubbles (Not alive but have some characteristics of living cells .They had SELECTIVELY PERMEABLE MEMBRANES.)

• Endosymbiotic theory: The belief is that eukaryotes formed approx. 2 billion years ago from COMMUNITIES of PROKARYOTES. Prokaryotes “moved into” prokaryotic cells. Created a symbiotic relationship. One group was able to use oxygen to make ATP Mitochondria. One group was able to use light to make sugars (Chloroplasts)

Rocks and Records of History

• What does Igneous, Sedimentary and Metamorphic rocks tell you about earths history? Igneous Rocks: Formed from cooled molten material, they indicate volcanic activity and the conditions that were present when they solidified. Sedimentary Rocks: They record the history of sediment deposition, environments, and may contain fossils that indicate past life forms and ecosystems. The different types of sedimentary rocks (biogenic, chemical, detrital) reveal information about the Earth's surface conditions at the time of their formation. Metamorphic Rocks: Formed from the alteration of existing rocks under heat and pressure, they show the conditions that led to metamorphosis, often tied to tectonic activity and the geological processes that affect rock layers over time.

• Sedimentary divisions: Biogenic sedimentary rocks: sediment made of solid bits of organic material (whole or broken up) that gets deposited. Chemical sedimentary rocks: sediment is in the form of dissolved bits (ions) that precipitate out of water.Detrital (also called "siliciclastic" and "clastic") sedimentary rocks: sediment is grains of various sizes weathered from previously existing rock, cemented together by minerals in the groundwater very commonly produced in terrestrial and near-shore environments(By far the most common in which dinosaur fossils are found).

• Detrital Sedimentary cycle: Uplift – exposure to surface elements, Source rock experiences erosion, Sediments – transported by water, wind, glacial ice, etc., Deposition occurs, and the Lithification process causes sediments to cement into rock

• Paleoenvironmental clues: Roundness, sorting, and maturity in a detrital sedimentary rock = relative distance to the source. Energy of the environment = how fast the water or wind was moving which makes different-sized particles. Quiet water (lagoons, lakes, deep oceans)

  very fine-grained sediments. Faster moving water, and wind deposits large amounts of sediments quickly, more likely to bury large objects (such as the dinos).

Terrestrial Sedimentary Environments

• What are facies: (appearance): are the sets of characteristics(lithologies, sedimentary structures, suites of fossils) that represent a particular depositional environment.

• What are the types of terrestrial sedimentary environments

Terrestrial Depositional Environments: River Systems

• What is Walther's law: As depositional environments migrate laterally, the sediments of one environment come to lie on top of sediments of the adjacent environment. Patterns of facies throughout the years

• 2 types of fluvial rivers: Braided streams - horizontal beds of conglomerates and sands with unidirectional crossbeds, almost no mud. Meandering streams - Stream channels migrate downstream over time. Produce very distinctive sediments:Channel conglomerates. Cross-bedded channel sandstones, well-sorted Pointbar sands, somewhat finer than channel sands. Levee sands, ripple marks and finer grains. Backswamp, non-laminated mudstones. Cut-off meanders (ox-bow lakes) with lacustrine sediments. Additionally, meandering stream sequences surrounded by flood-plain deposits of paleosols interrupted by layers of flood muds. The whole package of stream deposits, paleosols, and ox-bow lakes form fluviolacustrine deposits.

• Deltas and types: Deltas are modified in shape by waves, tides, and

  stream forces, but produce same general facies of different sedimentary environments from inland towards the water body.Topsets (delta plain): sand and silt, nearly horizontal, cut

  through with stream channel deposits and with paludal

  facies, will contain terrestrial fossils. Foresets (delta front): grade into silt and clay, slope seaward, will contain marine fossils, but also some material washed in from terrestrial environment. Bottomsets (prodelta): clay, horizontal beds, marine fossilsdominate

Coastal & Marine Environments: Sedimentary Deposition

• Transgression vs regression and the pattern of sediment deposition: Transgression - Rising sea levels flood land, depositing deeper marine sediments over shallower ones. Regression - Falling sea levels expose land, leading to shallower deposits on deeper ones.

• Coastlines: Coastlines are important: give us the interface between marine and terrestrial conditions: and can move inland or seaward very quickly. Coastlines are ephemeral: they move towards the ocean basin or towards the continent due to a number of factors.

Age of Rocks: Absolute Dating

• Difference between absolute and relative dating: Absolute dating is the actual age of the rock that occurs through radioactive dating. Relative dating is determining the age of rock layers or fossils based on their position underground.

• Which rock is the best to use for radiometric dating and why? Igneous rocks are the best because when they form, minerals often contain only a parent isotope and none of the daughter isotope.

• How do scientists tell the actual age of rocks? Radioactive dating by measuring the age of the material by comparing the amount of decayed radioactive elements present in them.

• You will need to calculate the half-life.

Relative Dating and Relative Dating part 2

• 6 principles: Principles of Superposition: The oldest layer is on the bottom, and the youngest is on the top. Principle of Original Horizontality: Rocks/Sediments are deposited horizontally, later forces will push and tilt, and reflect tectonic forces and weathering and erosion over the years. Principle of Lateral Continuity: Once sediments have been deposited, erosion occurs throughout a large area which takes away the layers of rock. The layer beside the lateral continuity is still the same age as before. Principle of Cross-Cutting Relationships: Igneous intrusions or faults are younger than the rock it cuts across. Principle of Inclusions: Rock fragments in a layer are older than the rock itself. Determines which layer is the oldest upon the inclusions. The principle of fossil succession states that fossil organisms succeed in one another in a definite and determinable order. Therefore, any time period can be recognized by its fossil content.

• Which fossils would be best for index fossils (amount of time): Index fossils are widespread geographically, are limited to a

  short span of geologic time, and occur in large numbers.

  Geographically widespread, Existed for a short geological time, Easily identified, and Abundant

Reading assemblage zones

• Determining time sequence of cross cutting sections and identifying 6 principles

• What is an unconformity be able to identify the 3 types: Unconformities: Surface which represents geological time not represented in the rock record. (Three Types) Disconformity: Surface of erosion or nondeposition between beds that are parallel to one another. Wavy surface on top of flat surface. Angular Unconformity: Erosional surface on tilted or folded strata over which younger strata are deposited. Layers are always deposited horizontally and then shifted. Nonconformity: Erosional surface cut into igneous or metamorphic rocks, overlain by sedimentary rocks.