Slides (Pre-Midterm) Flashcards
What are the 7 principles of relative dating in geology?
Superposition: Oldest layers are on the bottom, youngest on top in undisturbed sequences.
Lateral Continuity: Layers extend in all directions until thinning out or meeting a barrier.
Original Horizontality: Sediments are initially deposited horizontally.
Cross-Cutting Relationships: Features like faults or intrusions are younger than the rocks they cut through.
Inclusions: Rock fragments within a layer are older than the layer itself.
Faunal Succession: Fossils follow a recognizable order in the rock record.
Correlation: Rock layers can be matched across locations based on composition or fossils.
What are the three types of unconformities?
Angular Unconformity: Flat-lying strata overlie tilted or folded rocks.
Nonconformity: Sedimentary rocks overlie igneous or metamorphic rocks.
Disconformity: Erosion or non-deposition separates layers of similar flat-lying strata.
What are the three types of unconformities?
Angular Unconformity: Flat-lying strata overlie tilted or folded rocks.
Nonconformity: Sedimentary rocks overlie igneous or metamorphic rocks.
Disconformity: Erosion or non-deposition separates layers of similar flat-lying strata.
How is geological time divided?
Eons: Hundreds of millions to billions of years.
Examples: Hadean, Archean, Proterozoic, Phanerozoic.
Eras: Tens to hundreds of millions of years.
Examples: Paleozoic, Mesozoic, Cenozoic.
Periods: Millions to tens of millions of years.
Examples: Cambrian, Jurassic, Quaternary.
Epochs: Hundreds of thousands to tens of millions of years.
Examples: Paleocene, Miocene, Holocene.
Ages: Thousands to millions of years.
What are the major eons and their significance?
Hadean: Time before the rock record; “Hell-like” conditions.
Archean: Origin of life; earliest known rocks.
Proterozoic: “Earlier life,” emergence of multicellular organisms.
Phanerozoic: “Visible life,” abundant fossil records of complex organisms.
What is stratigraphy, and why is it important?
Stratigraphy is the study of rock layers (strata) and their arrangement. It helps reconstruct past environments, determine the origin of sediments, and understand geological time through correlations and relative dating.
What are sedimentary facies?
Sedimentary facies are distinct sequences of sediment within a depositional environment that share specific characteristics like composition, grain size, and fossil content. They reflect changes in environmental conditions.
What are mobile agents, and how do they affect sediment transport?
Mobile agents include water, wind, ice, and gravity. They move sediments from their source to deposition sites. High energy moves larger particles; low energy deposits smaller ones.
Who were key contributors to geology and their contributions?
Nicolaus Steno (1686): Principles of superposition, original horizontality, and lateral continuity.
James Hutton (1797): Proposed uniformitarianism, laying the foundation for modern geology.
Charles Lyell (1875): Expanded uniformitarianism and introduced “Principles of Geology.”
William Smith (1839): Developed the concept of faunal succession and created the first geological map.
What are common sedimentary structures, and what do they indicate?
Ripple Marks: Indicate water or wind movement.
Cross-Bedding: Formed by shifting currents in water or air.
Mud Cracks: Suggest drying and shrinking of wet sediment.
Graded Bedding: Indicates deposition from a settling current.
What are key concepts in radiometric dating?
Alpha Emission: Releases a helium nucleus.
Beta Emission: A neutron becomes a proton, emitting an electron.
Half-Life: Time for half of a radioactive isotope to decay.
Closure Temperature: Below this, isotopes are locked into a mineral.
What is the theory of plate tectonics?
It states that Earth’s crust is divided into large plates that move on the softer layer beneath, causing geological phenomena like earthquakes, volcanoes, and mountain formation.
What are the three types of plate boundaries?
Divergent: Plates move apart, forming mid-ocean ridges and rift valleys.
Convergent: Plates collide, causing subduction, mountain building, and volcanic activity.
Transform: Plates slide past each other, causing earthquakes.
Where did early life on Earth likely originate?
Early life likely originated near hydrothermal vents in warm, chemically enriched ocean environments, where sulfur-reducing bacteria thrived.
What are stromatolites, and why are they significant?
Stromatolites are layered structures formed by cyanobacteria. They are significant as the earliest reef-forming organisms, dominating Earth’s ecosystems for 2 billion years.
