Historical Geology Exam 2

What is a Subduction Zone?

A region where one tectonic plate slides beneath another, typically when a denser oceanic plate is forced under a lighter continental plate.

Oldest and coldest get recycled; cannot subduct continental plates.

What are divergent boundaries

plates separating and new oceanic lithosphere is forming as magma rises from the mantle to the surface.

What are convergent boundaries?

tectonic plates collide, and the leading edge of one plate decends beneath the margin of other plate.

what are transform boundaries?

tectonic plate boundary where two plates slide past eachother. crust is not created or destroyed.

Modern examples of divergent, convergent, transform boudaries?

Diverget: Mid oceanic ridge

Convergent: Himalaya mountains

Transform: San Andreas fault

What are mountains and which plate tectonic enviroment do we see them forming?

natural elevations of the earths surface and are formed at convergent boundaries where plates move toward eachother.

Himalayas are modern example of mountains forming today.

Convergent Boundaries

Where do we see volcanoes in plate tectonics and how do they form?

volcanoes are found at tectonic plate boundaries in convergent and divergent boundaries and at hotsposts magma from beneath the earths surface rises and erupts.

where do earthquakes occur, and why?

along plate boundaries tectonic activity causes stress, found in all boundaries

What are the driving mechanism of plate tectonics?

• Convection currents: heat from earth core create slow, circular movements in the mantle that carry the tectonic plates above them.

• Ridge push: gravity pushes oceanic lithosphere away from the higher spreading ridges and toward the trenches, where it is subducted back in the earths interior

• Slab Pull: the subduction cold slab of lithosphere, being denser than the surrounding warmer asthenosphere pulls the rest of the plate along as it descends into the athenosphere

Who is considered the founder of modern geology?

James Hutton “present is key to the past”.

What is super position?

sedimentary rocks that are undisturbed, the oldest rocks at the bottom and youngest at the top.

what is original horizontality?

layers of sediment are originally deposited horizontally

what is laterla continuity?

sediment extends laterally in all directions until it thins and pinches out

what is uniformitarianism?

changes in the earths crust during geological history have resulted from the action of continuous and uniform process.

what are cross-cutting relationships?

igneous intrusion or fault must be younger than the rocks it intrudes or displaces.

History on determining the age of earths?

• lord kelvin estimated the Earth had been cooling at 20 to 400 million years ago

• salt in water

• uniformitarianism

what was the game chnager on determining the age of earth?

Radioactivity

What are radiometric isotopes?

atoms of an element with a different number of neutrons, which makes their nucleus unstable

What are parent and daughter products?

a parent product is the original unstable isotope, and daughter product is the new often more stable isotope that is formed after the parent decay

What is Half-life

the time it takes for one-half of the atoms of the original unstable parent element to decay to atoms of a new more stable daughter element

How isotopic dating works, how to calculate it?

calculations of the given daughter or parent. Minus 100. then find how many half lives it has passed. 100= 0 lives, 50 = 1 and so on. then multiply the number of half lives times the number of value of a half life.

Which rocks can be dated and which ones cannot

• Can: igneous rocks

• Cannot: sedimentary rocks, meteorites, metamorphic rocks

What are other dating techniques?

Relative dating: process of determining the chronological order of events, rocks, or fossils by comparing their age to one another.

absolute dating: determining the precise age of the rock

Geologic time scale

Study time scale

principles of inclusions, and baked contacts

inclusion: rock fragments (inclusions) within another rock are older than the rock that contains them

baked contacts: rock surrounding an igneous intrusion is older than the intrusion itself because the heat from the magma metamorphoses, or "bakes," the surrounding rock.

What are the various types of stratigraphy?

Litho- age based on rocks

bio- age based on fossils

chemo - age based on chemistry

magnetostrat- age based on polarity

know the 3 tyoes of unconformities

unconformities - represents gaps in the geologic record

• angular unconformity: present if strata below an erosion surface are inclined at some angle to the strata above

• disconformities: an erosion surface in sedimentary rocks that separates younger rocks from older rocks both of which are parallel to eachoter

• non conformity: an erosion surface cut into plutonic rocks or metamorphic rocks that is overlain by sedimentary rocks.

What are transgressions

sea level rises with respect to land (lime stone at the top)

what are regressions?

sea level falls with respect to land (sand stone at top)

how to indentify transgressions and regressions in rocks?

order of the sediemtn helps to identify

how do fossils form?

form when a dead organism is burried fast preventing decomposition, scavenging, hard parts fossilized best.

What are the types of fossils?

• replacement: original hard parts of an organism have been dissolved and filled with new minerals

• mold fossil: a mold fossil is the impression left in sediment by an organims

• internal fossil: formed when the mold is filled with minerals or sediment

• permineralization: pore spaces are filled with minerals 

• carbonization: carbon film left behind

• unaltered remains: no change in composition or structure organism

• trace fossil: evidence of the presence of an organism but no remains.

Glen rose trackway

predator prey relationship, trace fossil

what is faunal succession?

principle that fossil organism succeed one another in a specific, predictable order in the rocks record.

what is an index fossil?

organism that was present during a particular time in earths history

Sedimentary rock properties

layered structures (strata), visible grains or particles, and the frequent presence of fossils

sedimentary structures

• cross bedding: individual beds are deposited at an angle to the surface upon which they accumulate

• mud cracks: polygonal fractures, when mud dries

• graded beds: change in energy in a location

• bioturbation: intense activity of organisms disrupts sediments.

Different depositional enviroments

• continental enviroments:

• marine enviromentas:

• transitional enviroments:

Types of sedimentary rocks

• clastic rocks: formed from pre-existing rock fragments (clasts) that have been weathered, eroded, transported, and cemented together

• chemical rocks: form from the precipitation of minerals from a solution, typically water, through evaporation or changes in temperature and acidity

• biochemical rocks: formed by the accumulation of the remains of living organisms, such as shells, skeletons, and plant matter

interpretation of depositional environments

analyzing sediment characteristics like rock type, sedimentary structures, and fossils to understand the past physical, chemical, and biological conditions where sediments accumulated.

Glacial till

Glacial till is an unsorted, unstratified mixture of clay, silt, sand, gravel, and boulders deposited directly by a glacier. It is formed from material eroded and carried by the ice, which includes both fine particles from grinding and large chunks from plucking. Because it's deposited by the ice itself, the sediments are a jumbled mix of sizes, with angular, sharp fragments because they haven't been rounded by water transport. 

Alluvial fan

An alluvial fan is a fan-shaped landform made of sediment deposited by a stream emerging from a steep, narrow valley onto a flat plain. These landforms are created as water slows down and drops the rocks, sand, and mud it carried, with the most common hazards including sudden and destructive floods, debris flows, and mudflows.

Aeolian ( desert dunes)

Aeolian landforms, or Eolian landforms, are produced by either the erosive or depositive action of wind. These features may be built up from sand or snow, or eroded into rock, snow, or ice.

How do we classify different sedimentary rocks?

• clastic rocks

• chemical rocks

• biochemical rocks

What are tongue stones

shark teeth

How are sedimentary rocks used in historical geology?

it can tell you about the ancient environment in the area

Greeks

Recognized all animals were basically built the same way.

Western thought

All animals and plants were created as we see them, no possibility for change.

Linnaeus

saw order in the natural worlds, originally proposed the linae classification system.

Species

organisms that can interbreed and produce fertile offspring.

Buffon

Defined species as: distinct animals that cannot interbreed to produce viable offspring. credited with bringing the idea of evolution into the scientific realm. established the idea of inheritance and adaption.

Cuvier

worked on modern and fossil vertebrates and ITS THE FATHER OF VERTABRATE PALEONTOLOGY.

Lamarck

coined the term biology, nature is constantly changing. change is fundamental,

Darwin

theory of evolution by natural selection, which explains how species change over time from a common ancestor. His work, particularly in the 1859 book On the Origin of Species, proposed that organisms with advantageous traits are more likely to survive and reproduce, passing those traits to their offspring.

Galapagos Finches

evolved from the same species but chnaged due to different enviroments

Natural selection

Natural selection is the process where organisms with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits to their offspring

Mendel

1860s: Mendel’s breeding experiments with garden peas showed how variation is maintained and passed on.
Traits are controlled by genes
Genes that control traits do not blend during inheritance
Genes are not lost even though not expressed in every
generation

microevolution

evolutionary change within a species or small group of organisms, especially over a short period.

Macroevolution

large-scale changes over long periods, such as the origin of new species, the evolution of major new traits, and the extinction of entire groups

phyletic gradualism

theory of evolution proposing that species change slowly and steadily over long periods through the accumulation of small, incremental changes, rather than through rapid bursts

Punctuated equilibrium

hypothesis that evolutionary development is marked by isolated episodes of rapid speciation between long periods of little or no change.

Parallel evolution

develop similar characteristics in closely related organisms

Divergent evolution

many organisms evolving from common ancesto

Convergent evolution

develop similar characteristics in distantly related organisms

Clades

a group that has a single common ancestor

prokaryotes

single-celled organisms, such as bacteria and archaea, that lack a nucleus and other membrane-bound organelles.

eukaryotes

Eukaryotes are organisms whose cells have a distinct nucleus and membrane-bound organelles, such as mitochondria

Evidence for evolution

• direct evidence of small scale changes within a species: selective breeding aggriculture, natural population shifts

• direct evidence of large-scale changes from the fossil record: transitional forms

• homologies: similar structures derived from a common ancestor

• vestigal structures: baggage left over from ancestors

• atavism: characteristics of their ancestors

Survival of the fittest

Does not mean the fastest, strongest, etc.,
Means the best well suited for the environment at that time

how evolution works

through gradual changes in inherited traits in a population over generations, primarily driven by the mechanisms of natural selection, mutation, genetic drift, and gene flow

what does evolution mean

the process by which animals, plants, and other living organisms are transformed into different forms by the accumulation of changes over successive generations.

mendel and genetics

known as the father of genetics for his pea plant experiments, which established the fundamental principles of inheritance, now known as Mendelian genetics.

what evidence supports evolution

ossil record, comparative anatomy, biogeography, embryology, and molecular biology (genetics), as well as direct observation.

what fossils tell us about evolutions

show that life has evolved by providing a timeline of past life through rock layers, demonstrating gradual change over time, revealing transitional fossils that link different groups, showing that extinction is a natural process, and illustrating the development of new traits and adaptations

which environment would most likely produce sedimentary deposits charcterized by very well-sorted, very well-rounded grains that are nearly pure quartz.

beach

glazial till is composed of ——- sized particles

clay to boulder

medium-sized frosted sand grains and large-scale cross-beds indicate —— environment

dunes

siltstone containing marine fossils likely formed in a ——— enviroment

shallow marine

swamps, channels, floodplains, and submarine slopes all play a role in the development of

marine deltas

what type of sediment is found in a deep marine setting

clay

analysis of —— is the best way to determine depositional environments

seidmentary structures