Historical Geology Exam 1

Test 1

What is the Scientific method?

The process of making an accurate, reliable, consistent, and non-arbitrary representation of the natural world.

How does a Theory get proposed?

After a Hypothesis is tested multiple times, and its found then, its proposed as a theory.

Can a Theory be rejected? if so how?

Yes

If new research is found and it contradicts the previous.

What is Historical Geology

The study of origin and evolution of earth, its continents, oceans, atmosphere, and life.

Why study Historical Geology?

by studying historical geology we can determine what happened in the past, additionally to be able to explain why those events happened.

Atmospheric composition, how it differs from other planets

We have an atmosphere and we have high levels of Nitroger - 78% and Oxygen 20.95%, giving us the right conditions to have life.

Greenhouse effect

Gases in the Earths atmosphere trap heat, preventing it from scaping keeping the planet warm.

examples of greenhouse gases are.

• water vapor

• Carbon dioxide (CO2)

• Methane (CH4)

Carbon Cycle

continuous movement of carbon atoms among the earth’s atmosphere, oceans, land, living organisms.

Carbon Sinks and Sorces

Sinks

• Oceans

• Forests

• Volcanism

• Methane from the melting of permafrost

• Soils

Sources

• Coal

• Biomass Burning

• Subduction Zones Of limestone

Weather VS Climate

Weather: short term temperatures - Day to Day

Climate: long term temperatures, precipitation - impacts decades

Long Term processes that affect Climate

• position of continents

• uplift of land surfaces

• formation of coal and oil

• evolutions of life forms

• volcanism

Short Term processes that affect Climate

• Milankovich Cycles

• Surface albedo

• vocanism

• solar radiation output

• oceanic circulation

Ocean Currents

They help recirculate heat

Why is the ocean important

ocean is a heat sink, prevents the land from becoming too hot.

how do we study climate change

• proxies

• ice cores

• sediments

Greenhouse gases

Carbon Dioxide (CO2)

Methane (CH4)

Water Vapor

Concentration of greenhouse gases in the past and today

C02 lower in the past, today is high

what are milankovich cycles?

these are changes in the earths movement, shape of its orbit around the sun, the angle of the earths axis, the direction earths axis of rotation is pointed.

Albedo?

how much sunlight does a surface reflects

Silicate weathering is important for long-range control of carbon dioxide

another form of trapping carbon (carbon sink). particles of carbonic acid go to form limestone.

what is current rate of carbon dioxide change vs historical trends?

is much higher after the industrial revolution, carbon dioxide levels skyrocketed to 422 ppm.

why is the earth not heating up more with current carbon dioxide levels?

heat is absorbed by the oceans.

Definition of a mineral

• naturally ocurring

• inorganic

• crystalline structure

• a defined chemical composition

• distinctive physical solid

What are atoms

smallest fraction of an element with all characteristics of an element

• protons +

• electrons -

• neutrons

What are Isotopes

Variation of an element that differs in the number of neutrons

examples

• oxygen 18

• oxygen 16

  oxygen 18 is heavier

What are Ions

An Atom that is not electrically neutral

Types of chemical bonds

Ionic Bonds - Easily brekable

Covalent Bonds - hard to break

Metallic Bonds - free floating valance electrons

Rock VS Mineral

a mineral is the foundation of a rock

a rock is composed of one or more minerals

what is a crystal structure?

atoms arranged in a specific 3 dimensional framework, in a crystaline material

what are some physical properties of minerals?

• hardness

• streak

• clevage

• color

• luster

• crystal form

how are minerals classified?

most are classified by chemical composition and crystal structure

most in groups

• native metals

• carbonate minerals - CO3 anion group

• Silicate Minerals - silicate anion group

3 rock types?

3 rock types

• igneous

• sedimentary

• metamorphic

how to distinguish the 3 rock types?

Igneous Rocks - formed from the cooling and solidification of molten rock (magma or lava)

2 types: Plutonic/intrusive, Volcanic/extrusive.

classified by their crystal size and composition (felsic/mafic)

Sedimentary Rocks - form when solid or dissolved materials are transported elsewhere as sediment.

3 types:

• Detrial Rocks: made of detritus, solid particles (gravel, sand, mud).

• Chemical Rocks: made of minerals derived from materials in solution and extracted by an inorganic chemical process.

• Biochemical Rocks: mostly made up of biomaterials from organisms

Classified into these 3 group

Metamorphic Rocks - formed under specific conditions, changed by heat/pressure, but not melted. New minerals may be formed, minerals are aligned texturally, a combination of mineralogical and texture (foliated).

3 types of metamorphism

• Regional - takes place in large but elongated areas as a result of high pressure, deep burial, foliated rocks.

• Contact - takes place when heat and fluids from an igneous body alter adjacent rocks, proximity to molten rock, and non-foliated are most common.

• shock - rapid applications of extreme pressure

distinguished by being foliated or not foliated

intrusive vs extrusive rocks

• intrusive rocks form from magma cooling down slowly, belows earth surface generating larger and more visible crystals

• extrusive rocks form from lava that cools rapidly in the surface creating small microscopic crystals

how are rocks classified

chemical composition and texture

know the sedimentary rock types and how they are formed

• Detrital rocks are formed from detritus, solid particles (gravel, sand, mud).

• Chemical rocks are formed when dissolved minerals come out of the water through evaporation or precipitation, leaving behind solid minerals that eventually turn into rocks

• Biochemical rocks are formed from living organisms

What is lithification?

geologic process of converting sediment into sedimentary rocks

What are volatiles?

substances like water, carbon dioxide, and sulfur compounds that vaporize at normal temperatures and pressure

what is a protolith?

a protolith is the starting rock before metamorphism

what is foliation and how does it form?

parallel alignment of platy minerals due to direct pressure, crystals are aligned perpendicular to the direction of stress

hwo do we get non-foliated textures?

no pressure, no aligment, recrystalized, contact metamorphism

what is regional metamorphism? examples

takes place in large but elongated areas as a result of high pressure, deep burial, creating foliated rocks

examples are

• slates

• schist

• gneisses

what is shock metamorphism? examples

rapid applications of extreme pressure, such as meteor impacts.

examples are

• bediasites

• shocked quartz

what is contact metamorphism? examples

takes place when heat and fuids frorm an igenous bodyt alter adjacent rocks, proximity to molten rock, non-foliated are the most common.

examples are

• quartzite

• marble

tectonic enviroments for different rock types

Igneous rocks are formed at convergent and divergent plate boundaries where magma generates and cools.

Metamorphic rocks are found at convergent plate boundaries, within fold mountain belts, and in other areas with high heat and pressure.

Sedimentary rocks form on the Earth’s surface and are most abundant at convergent boundaries, but can form anywhere.

what is the differentiation of earth?

mantels, crust, core

how does earth differentiate? waht is the evidence?

started through density

evidence is the moon and seismic data

what is the source of earths internal heat?

radiactive decay and residual heat

how do siesmic waves behave, P-waves and S-waves

P-waves travel at high velocity when they hit a liquid they low down and bend

S-waves trave at a lower velocity once they hit a liquid they stop

Chemical properties of crust vs the whole earth

Crust has 8 elements and Oxygen is the dominant

Earth has 4 elemnts and Iron is the dominant

Wegner’s continental drift theory and evidence he provided

Continents drifted from a supercontinent, “Pangaea,” into where we see them now

evidence

• matching profiles of continental margins

• similar rock types and structures

• glacial deposits

• fossil evidence

Why was Wegner’s theory rejected?

not well recieved, ludicrous

no evidence on how the continents moved

What are climate belts?

physically being able to see climate indicators in rocks

How did the plate tectonic theory develop, and what evidence supports it?

developed in the 40’s and 50’s by the military when mapping the seafloor using sonar and magnetometers.

Evidence

• seafloor spreading

• mapping of the ocean floor, revealing magnetic properties

what is the age of oceanic crust?

relative to the continental crust, is much younger

who is hess and waht is his essay in geopoetry?

hess was a geology professor and naval officer

proposed the theory of sea floor spreading

what are magnetic reversals and how they form?

when the south and north magnetic poles switch

what is oceanic crust made of?

basalt