Earth 119 Exam 1 -Umich

What is the currently accepted age of the solar system in years?

4.6 billion years

The age of the oldest ocean floor is about?

170-200 million years old

The best estimate of the age of the Universe is about ___ years.

13.7 billion years

Which characteristics of Earth's magnetic field played a major role in establishing the

theory of plate tectonics?

It reverses polarity, unique polar wander paths of continents

Red shifts noted in the radiation spectra of celestial objects show an expanding universe

are analogous to the _____ effect observed as train passes an observer.

doppler

What are some observations that support the theory of tectonic plates on Earth?

Fossils, matching geologic units, fit of continents, climate belt distribution, locations of past glaciers, seafloor magnetic reversal record

Why does plate tectonics and seafloor spreading occur? Think in terms of what it does

to the heat budget of the Earth.

Gravity on denser plates, convection

What geologic features or phenomena are present at divergent plate margins?

Ridges, new seafloor creation, magma rises, solidifies, and moves.

What are the 8 most abundant elements in the Earth's crust?

Oxygen, Silicon, Aluminum, Iron, Magnesium, Calcium, Potassium, Sodium

What are some mechanisms or factors which lead to the minerals crystallizing from a

magma (or water).

Magma rises and gets exposed to cooler temperatures.

What is the most abundant mineral group present in the Earth's crust and mantle?

Silicates

What are the requirements for a solid to be classified as a "mineral"?

Naturally occurring, formed by geological processes, crystalline, definable chemical composition

Solids that do not possess an orderly arrangement of atoms (frequently cause by very rapid

cooling) are called _______.

Glass

What is the chemical formula for the mineral Quartz?

SiO2

We are some measurable and observable properties of minerals that help us distinguish among them?

Hardness, color, luster, taste, cleavage/fracture, streak, specific/gravity

What do we call the building block for most silicate minerals and what is its chemical formula?

Silica tetrahedron (SiO4)4-

In silicates, the building blocks or silicon and oxygen can be arranged in a crystal in many ways. What are the five different arranges of these building blocks?

isolated/independent, single chain, double chain, 2D sheet, 3D framework

In nature we can have two different minerals even though the chemical composition is identical because they have a different crystal structure. What do we call these - for example aragonite and calcite (bot CaCO3)?

Polymorphs

The Earth is constructed with 4 major realms reflecting different compositional and physical

characteristics. What are the approximate depths to the boundaries between each of these?

Crust(10-70km), mantle(3000km), outer core(5000km), inner core(6370km)

What is the "asthenosphere" and why is it important when considering plate tectonics and

seafloor spreading?

The asthenosphere is the part of the mantle that can flow when acted on by a force. The lithosphere floats on this, and this is what allows the plates to move around.

When minerals are broken, this breakage can occur along planes of weakness within the crystal. What do we call this property?

cleavage

proposed the concept of continental drift?

Alfred Wegener

Atomic weight = ____ + _____

protons and neutrons

What is the rock name of a coarsely crystalline igneous rock composed of abundant quartz, K-Feldspar (Orthoclase), Muscovite?

Granite

What is the rock name of the same composition , but wi0th very fine crystals (an extrusive rock)?

Rhyolite

If I have a rock with a little olivine, Ca-Plagioclase and Pyroxenes, and it is coarsely crystalline,

what is its rock name and is it a mafic or felsic rock.

Gabbro, mafic

The crystallization of mafic igneous rock begins at much higher temperatures than for felsic

minerals. What are the respective temperatures for these?

Mafic: 1200 C. Felsic: 600 C

Volcanic rocks (extrusive) have much small crystal sizes than intrusive rocks. Why?

They cooled fast.

Mafic igneous rocks occur at which kinds of lithospheric plate interactions?

divergent plate boundaries and hot spots in the ocean

Felsic and intermediate igneous rocks occur at which kinds of plate interactions?

ocean-continent or ocean-ocean convergent boundaries, land hot spots

You should have "Bowen's Reaction Series" imprinted in your memory. What minerals would

you expect to find in an ultramafic rock versus a felsic rock?

Ultramafic: olivine. Felsic: Quartz, orthoclase feldspar.

What is the intrusive rock name equivalent to an "andesite" extrusive rock?

Diorite

What is the extrusive rock name equivalent to an intrusive "granite".

Rhyolite

What is an igneous dike and how does it differ from and igneous sill?

Sills: flat, window sill like structures formed by horizontally intruding igneous rocks. Dikes - Same thing but breaks through sills and vertical.

At seafloor spreading centers, what kind of igneous rock is erupted and what distinctive

structure does it form?

Basalt; pillow basalt

Why is the Earth continuing to produce heat in the mantle? What kinds of reactions make this heat?

Radioactivity; radioactive decay

If you were to look at a map of the world's tectonic plates, could you identify which ones are

convergent, transform or divergent?

What is the radius of the Earth? The distance from its surface to the center of the core?

6400 km

Chemical Bonds are primarily controlled by interactions among electrons. What are the two

types of bonds, what characterizes each and which is forms the strongest bonds?

Covalent: share electrons, STRONGER. Ionic bond: transfer electrons, MORE ABUNDANT

The Wilson cycle basically says the the World alternates between forming super continents

which are then broken up, only to reform new super continents in the future. The last super

continent was called Pangea (about 250 Ma --million years ago). What was the name of the

supercontinent that existed about 1 billion years ago?

Rodinia

What physical conditions transform other rocks into "metamorphic rocks"?

high temperature, high pressure, really hot fluid

What two mechanisms are responsible for the formation of magmas?

Decompressional melting: temp stays same but pressure decreases. Flux melting: adding volatiles to lower melting point

Magmas can change (evolve ) in their composition as they ascend through the lithosphere.

What are the mechanisms that can lead to this change in composition?

Partial melting(minerals w/ lower melt temp coming off) and Fractional crystallization/differentiation(mafic rocks take out minerals as they cool and sink)

When the Universe formed after the Big Bang, what elements were most abundant directly after its formation?

H and He

Other elements formed by a process called nucleosynthesis. What is this and where does this occur?

It's a series of fusion reactions that occur in stars.

What is accretionary heating, and how did it lead to the density stratification of the Earth

(Formation of the Core, Mantle and Crust)?

pushing something into tight space releases energy. The denser stuff got pushed to the core while the lighter stuff stayed above it.

What is the accepted age of our Universe (not the biblical age).

13.7 billion years

How do we know the circumference of the Earth?

Utilizing angles of the sun

How do we know that the Earth is a sphere and not flat?

arcuate shadow on moon

How do we know the distance from the moon to the Earth?

Before: Earth's shadow on moon. Now: Reflectors on moon and lasers on Earth.

Based on fundamental principles of physics F=ma, and F=GmM/r2 ( you don't need these to calculate this!), it was determined that the Earth has an average density of 5.5 grams/cc.

However, the rocks that we observe from the mantle and the crust have a density of only 3.5

and 2.7 g/cc, respectively. Where is the extra mass (weight) and what is its composition?

The extra mass is in the core of the Earth. The composition is iron and nickel

What is the oldest age of the seafloor (ocean crust)? It is much younger that the age of the

Earth. What happened to all of the older seafloor?

170-200 million years old. The older seafloor was recycled due to cycle of subduction and seafloor spreading.

What is "isostasy"?

Iceberg effect

We now know that rigid lithospheric plates move (or drift) relative to one another, floating on a

asthenosphere that is plastic rather than rigid. How fast do plates move?

50 mm/year

What are the three kinds of boundaries between tectonic plates?

Transform, divergent, convergent

Continents can grow in size through time. Beginning as small continents that merge together

into larger plates. What are three ways continents "accrete?

Transform motion, microcontinents coming together, island arcs

What is the rock cycle, and how does one type of rock (i.e., Igneous) become another type (i.e.,

sedimentary or metamorphic)?

Rocks transitioning through time into different types of rocks. This can happen through erosion and deposition, burial and heating, melting, and subduction and melting.

I have shown pictures of a "Porphyritic Andesite". What is a porphyry and how does it form?

It is a rock with larger crystals embedded in finer grains. The larger crystals form as the rock is still in the earth and the finer crystals form as the rock forms above ground

How does the presence of water impact the melting point of minerals? Think about how we

form magmas?

Water can lower the melting point

What is decompressional melting and under what geologic setting is it responsible for the

formation of magmas?

Temp remains the same as it rises up from the the high pressure areas and melts due to the new lower pressure areas. It occurs at divergent boundaries.

What is a pillow basalt? Where does it form?

Type of igneous rock that forms at a seafloor spreading centers.

Columnar jointing, such as that phenomenon that created the structures in "Devils Tower" or

"Devils Causeway" forms by what process?

type of fracturing that yields roughly hexagonal columns of basalt; columnar joints form when a dike, sill, or lava flow cools.

What is a pyroclast?

debris from volcanoes

The deep red color of soils found in Georgia and other warm, humid regions is caused by the formation of _______ during weathering

Iron oxides

We name clastic sedimentary rocks based in part on their grain size. Going from largest grains to smallest sized grains, what is the order (ie., shale, conglomerate etc.)

Conglomerate, sandstone, shale

Mature clastic sediments are distinguished from immature sediments on the basis of what observational characteristics?

shape(round/angular), sorting(well or poor), Chemical composition

Water particles (or buoyant objects) move in what kind of pattern when moved by surface waves in water?

circular orbital fashion

Diurnal ocean tides occur twice a day in response to the ____________.

Moon

Which two sedimentary features listed below can be used to determine the velocity (speed) and direction of the flow of water?

erosion and deposition?(not sure if right)

Which of the minerals have a very low solubility at the Earth's surface and therefore is least susceptible to chemical weathering?

felsic(?)

In turbidites, we occasionally observe normally graded beds where the size of sediment grains is sorted with the coarsest grains on the ___________of the bed.

bottom

Which rock type is formed under high energy (fast flowing water) conditions? shales, sandstones or conglomerates?

conglomerates

Most shells or skeletons made by marine organisms are composed of which mineral group?

carbonates

The tendency for differences in current velocity to separate sediments into different sizes is called?

grading

What is an atoll and how does it form?

ring shaped coral reef that forms around a former underwater volcano that rose and sank.

Which of the following physical weathering process enlarges fractures and extends them deeper into large boulders and bedrock?

freeze-thaw weathering

When we examine the texture (shape) of clastic sedimentary grains, which shapes indicates that a sediment is more mature? (i.e., angular, sub-rounded, elongate, rounded)

rounded

What type of rock (igneous, metamorphic or sedimentary) are most abundant at the surface of the Earth?

igneous

What is the definition of a Sedimentary Rock?

formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation

What are processes of Chemical Weathering

oxidation, hydrolysis, carbonation

Which of the following minerals is most susceptible to weathering (Olivine, Na-Plagioclase, Quartz, K-spar [Orthoclase])?

olivine

When we chemically alter rocks, which minerals dissolve into water and serve as the building blocks for the formation of Chemical Sediments?

silica

What minerals weather to form Clays?

aluminum rich like feldspars

Under what orientation of the Moon-Sun system do Spring tides form?

Moon is either between earth and sun or behind earth

The energy of Surface Waves decrease with increasing depth. At what depth does the energy decrease to zero (wave base)?

below ½ distance between 2 crests(wavelength)

Common sedimentary bedforms include asymmetric ripples, dunes, etc. that have a shallow erosional side and a steeper depositional side. Which side is on the down current side, shallower or steeper side?

steeper

Under what physical conditions do Metamorphic Rocks form?

Temperature and Pressure and also Diffusion (Solid-state) processes

What mineral is responsible for the foliation developed in a metamorphic schist?

micas

Gneiss is a higher grade metamorphic rock that is distinguished from lower grade rocks by what characteristics?

temp and pressure under which it forms

What type of metamorphic facies is characteristic of a rock that has been in contact with an intruded magma at relatively shallow burial depths? Hornfels, Burial, or Blueschist

hornfels

What is solid-state diffusion?

Reordering of atoms into new minerals

Some metamorphic rocks do not develop foliation. Under what kind of stress are these rocks formed. These are characterized by interlocking small crystals, such as marble. (directed, normal or shear stress)

normal

How deep in the earth do rock have to be buried to reach 3kbars of pressure?

10km

If shales are progressively metamorphosed under increasing burial, what is the sequence of rock types that form as the metamorphic grade increases? Ultimately the highest grade is the formation of gneisses.

Slate -> phyllite -> schist -> gneiss

A blue colored mineral, Kyanite, is formed under which metamorphic setting? It is high pressure, but relatively low temperature

regional/contact metamorphism at collision or subduction zones

Garnets are present only in metamorphic rocks. True or False?

false