GEO 101 Exam 1

What is the current theory for the formation of our Solar System?

The Sun and planets condeensed from a cloud of gas and dust

Which of the following statements about the early universe is NOT true?

Complex elements like Carbon and Iron formed during the Big bang

The key evidence that the universe is expanding is

the red shift of light from distant galaxies

Which statement represents the favored geological theory describing the formation of the Earth?

The earth formed by the coalescence of planetesimals that occured in a ring orbiting the sun

According to the geocentric model

the earth lies at the center of the universe

Differentiation of the core from the mantle early in Earth's history was possible because theplanet was ____________ at the time.

very hot

Most asteroids inhabit the "asteroid belt" between the planets

Mars and Jupiter

In 2006, the International Astronomical Union produced a major announcement concering Pluto. What was it?

Pluto has been officially demoted from its former status as one of nine major planets in our solar system

Aside from Earth, the terrestrial (rocky) planets are

Mars, Mercury and Venus

According to the Big Bang theory

everything that now comprises the universe started at a single point about 13.7 billion years ago

Which of the following is NOT true of the mantle

Generates the Earth's magnetic field

Which of the following is NOT one of the driving forces for plate tectonics

Wadati-Benioff zone

A mid-ocean ridge IS an example of which of the following active tectonic plate margins?

Divergent margin

What is the largest of Earth's concentric zones by volume?

the mantle

The lithosphere is composed of the ____________.

crust and the uppermost part of the mantle

Wegener proposed continental drift after he observed evidence from fossils, glacial deposits, andthe fit of the continents that suggested all of the continents were once ____________

combined to form a supercontinent (he termed Pangaea) in the late Paleozoic through the Mesozoic

The Wadati-Benioff zone is a belt of earthquakes found

within a downgoing plate at a subduction zone

Most of the pushing force driving plate motion is produced

at mid-ocean ridges

Every plate boundary can be recognized by

the presence of an earthquake belt

At a transform plate boundary, two opposed plates

slide past one another

The most common mineral group within Earth is the (1 word)

silicates

Which of the following physical characteristics of minerals refers to the appearance of a mineral's surface under reflected light?

Luster

When we say that a material is "crystalline" we mean that internally

atoms are distributed in an orderly arrangement

Which of the following processes does NOT lead to the formation of a mineral?

Precipitation from an aqueous solution in the laboratory

The seven principle classes of minerals are distinguished from each other based on:

chemical composition

The fundamental unit of the most common mineral class on Earth is:

the silicon-oxygen tetrahedron

Clastic sedimentary rocks are primarily classified on the basis of

grain size

Which of the following IS an example of chemical weathering processes

Oxidation

Which of the following is NOT a characteristic used to classify clastic sedimentary rocks?

Cleavage

The single property that can be used to identify any mineral is ____________.

none of the above; multiple properties MUST be used to identify a mineral

Which of the four sedimentary laers in this figure is the oldest?

The layer on the bottom

Which principle of relative dating can be used at Siccar Point in Scotland todetermine that the rocks below the unconformity were tilted to vertical beforeerosion occurred?

Original horizontality

What type of feature is represented by the boundary between geologic units 2 and 3?

unconformity

Missing geologic time caused by erosion is called a (an)

unconformity

If a rock started with 1,000 atoms of a parent but now contains 250 atoms, how many half lives have passed?

2 half lives

Why don't these two sequences of fossil-bearing rocks match exactly?

they have different histories of erosion and deposition

This figure shows two sections that partially overlap in age. Dashed lines show how the two sections correlate. What can you conclude from these correlations?

the left section represents older rocks than the right section

What was the Big Bang?

14 billion years ago a cosmological event occurred that resulted in all of time, space, energy and eventually, matter.

What happened after the Big Bang?

The universe expanded quickly and cooled (inflation)

What is inflation?

A brief period of extremely rapid expansion of the universe immediately after the big bang

How were new elements formed?

Light elements (H, He) formed shortly after the Big Bang. Heavier elements were formed by nuclear fusion inside stars and during supernova explosions.

What is redshift?

The stretching of light to longer (redder) wavelengths as galaxies move away from us due to the expansion of space.

What is the doppler effect (in cosmology?)

The apparent change in wavelength of light due to objects moving away from each other.

What is the compositional structure of the Earth?

crust, mantle, outer core, inner core

What is the mechanical properties of the earth?

Lithosphere, Asthenosphere, Mesosphere (lower mantle), Outer Core (liquid), Inner Core (solid)

What is a plate?

A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust.

What are the three types of plate boundaries?

Convergent (collide), Divergent (move apart), Transform (slide past each other)

What is the driving force behind plate tectonics?

Slab pull (sinking dense plates), ridge push (gravity sliding from ridges), and minor mantle convection. (convection most used)

What geologic features are related to plate tectonics?

Mid-ocean ridges, trenches, abyssal plains, mountain belts, volcanoes, faults.

What was the hypothesis of Continental Drift?

The idea that continents were once joined together (Pangaea) and later drifted apart.

Evidence for Continental Drift?

1) continental fit, 2) similarity of fossil plants and animals, 3) similarity of rock sequences/formations, 4) paleomagnetism (glacial deposits across continents)

How is Earth's magnetic field generated?

By the geodynamo (turbulent movement of molten iron in the outer core.)

What is a mineral? (5-part definition)

A naturally occurring, inorganic, solid, with a crystalline structure and definite chemical composition.

What is a rock?

An aggregate (mixture) of one or more minerals.

What is the rock cycle?

the series of processes that change one type of rock into another type of rock

Difference between soil and sediment?

Sediment is loose rock fragments. Soil is sediment altered by weathering and biological processes. Soil has been modified by leaching or by accumulation of ions and may contain organic matter, whereas the sedi has not.

Difference between sediment and sedimentary rock?

Coherence: sediment consists of loose grains, sedimentary rock consists of a solid aggregate.

How is sediment generated?

weathering and erosion

How is sediment turned into rock?

Lithification through compaction and cementation.

Principal depositional environments discussed?

Rivers (fluvial) and beaches (coastal/marine).

Common sedimentary structures and what they indicate?

Ripples — water or wind movement

Cross-bedding — current direction

Graded bedding — decreasing energy

Mud cracks — drying conditions

How can ripples distinguish environments?

Symmetrical ripples → beach (wave action)

Asymmetrical ripples → river (one-directional flow)

Difference between relative and absolute age?

Relative age determines order of events.

Absolute age gives a numerical date (in years).

Principle of Uniformitarianism?

the present is the key to the past

Principle of Superposition?

In undeformed layers, oldest rocks are at the bottom.

Principle of Original Horizontality?

sedimentary rock layers are deposited in horizontal layers

Cross-cutting relationships?

A feature that cuts another rock unit is younger than the rock it cuts.

Intrusions and baked margins?

Igneous intrusions are younger than surrounding rock; surrounding rock is "baked" by heat.

What is radiometric dating?

Dating rocks using radioactive decay of isotopes.

What is a half-life?

the time taken for the radioactivity of a specified isotope to fall to half its original value.

How do you calculate number of half-lives passed?

Count how many times the parent isotope has been reduced by half.

How are fossils used to determine age?

Using first appearance, last appearance, fossil assemblages, and rapid evolution of index fossils.

What is an unconformity?

A gap in the geologic record caused by erosion or non-deposition.

What is a nonconformity?

Sedimentary rock overlying igneous or metamorphic rock.

What is a disconformity?

when two sedimentary rock layers are separated by an erosional surface

What is an angular unconformity?

Tilted/folded layers overlain by horizontal layers.

Which tectonic setting has the following melting mechanisms?

convergent margins matches devolatilization

divergent margins matches decompression

hotspots matches heating

At which margin type would you NOT find volcanoes?

transform margin

Which of these pairs are types of sedimentary rocks?

biogenic & clastic

The slide on the screen shows a series of sediments. Which order did these environments occur in?

Deeper ocean

Shallow sea/Shoreline

Beach

Shoreline/River system

Which of the following is NOT a manifestation of chemical weathering?

Breaking down of rocks by the growth of tree roots.

Which of the following is not a manifestation of a physical weathering process?

Water reacts with minerals and breaks molecules apart.

2 characteristics of a mineral

1) Naturally Occurring - A mineral must form through natural geologic processes. It cannot be man-made.

2) Crystalline Structure - A mineral must have an orderly, repeating internal atomic structure. The atoms are arranged in a definite geometric pattern.

Is ice a mineral?

Ice is a mineral because it is solid, has a crystalline structure, building blocks of rocks, naturally occurring, inorganic, and has a known composition.

Is volcanic glass a mineral?

No. It's not crystalline.

Name and describe two physical layers of the earth

Lithosphere - rigid, brittle outer layer, includes crust + uppermost mantle, broken into tectonic plates

Asthenosphere - soft, plastic layer beneath lithosphere, partially molten, allows tectonic plates to move

Describe how one type of unconformity form

Angular unconformity

1. Sedimentary layers are deposited horizontally

2. A tectonic event tilts or folds the layers

3. Erosion removes part of the tilted layers

4. New horizontal layers are deposited on top

How clastic sediment rock differs from another class

Clastic - made of fragments (clasts) of rock, formed by weathering, erosion, transport, and deposition (sandstone, shale, conglomerate)

Chemical - Forms from precipitation of dissolved minerals from water, often forms by evaporation, ex: gypsum

4 classes of sedi rock

Clastic, Chemical, Biochemical, Organic

Processes of Plate Margins (3 types)

Divergent (move apart) - new crust forms, mid-ocean ridges, shallow earthquakes, volcanism present

Convergent Boundary (plates collide) - ocean-continent, ocean-ocean, continent-continent

Transform Boundary (plates slide past) -strike-slip faults, shallow earthquakes, no volcanoes