GEOL-105 Pollev Questions: MIDTERM TWO

Order the layers of the Earth from top to bottom

Crust, mantle, outer core, inner core

Which layer of the Earth contains the geodynamo?

The outer core

What surface phenomenon expels water and gas to form the ocean and atmosphere?

Volcanism

Magma is a hot mix of different atoms. When it cools, some olivine minerals (Mg2SiO4) crystallize first. They form which rock?

Dunite

Igneous rocks form from the cooling of magma. What are examples of igneous rock?

Dunite, Granite, Basalt

In the following, which refers to a mineral, not a rock: Peridotite, Dunite, Olivine, Anorthosite

Olivine

One of the first minerals to form on rocky planets is anorthite, forming the plagioclase silicate rock anorthosite. What statement about anorthosite is correct?

It is lighter than typical mantle rocks

The second mineral to form massively on Earth was pyroxene, forming a rock that is now ubiquitous in the upper mantle. Which rock is it?

Peridotite

How does the rock basalt form?

By partial melting of peridotite, which eventually cooled into igneous rock

What is the most abundant rock at the surface of the rocky planets in the Solar System?

Basalt

What rocks are found at the Moon's surface, in particular in the Lunar Highlands and Mares?

Anorthosite (65%) and Basalt (35%)

Identify places on the Moon with a basaltic crust

The darker looking areas on the moon's surface

Basalt and Gabbro have the same composition, but different texture. Which one is Gabbro?

The glossier, sharper looking one (the one on the right of the image)

Even with the same composition, the aspect of lava flows differ by their temperature flow velocity. Which one is a'a flow?

The sharper, less smooth looking one (the one on the left of the image)

Order the elements of the oceanic crust from top to bottom

Sediments, pillow lava, sheeted dykes, gabbros

What is the typical density of the oceanic crust?

3 times that of water, 3,000 kg per cubic meter, 3 tons per cubic meter

What fraction of Earth's crust contains basalt?

About two thirds

How does granite form?

By cooling of magma depleted in magnesium and silicon

What is the average thickness of the continental crust?

35km

What is the average thickness of the oceanic crust?

6,000m, 6km, 6,000,000mm

What is isostasy?

A force that maintains continents above the seafloor, similar to buoyancy, the force that maintains lighter rocks above denser ones, a type of gravitational equilibrium

This is a bathymetric and topographic map of Earth. Click on a large region representative of the oceanic crust

The dark blue regions of the map

What are the three major types of rocks?

igneous, sedimentary, and metamorphic

What are the processes to create a sedimentary rock?

Compaction, cementation, and lithification

What features can help indicate a sedimentary rock?

The presence of fossils, bedding which occur by sediment deposition in layers, poorly sorted gran size (clasts of varying size)

Which type of rock forms by a change of state?

Igneous

What is the principle of uniformity (uniformitarianism) in geology?

The same processes and laws that we observe today also operated during Earth's history

What is an angular unconformity?

Angular contact between two rock strata of different ages

Where is the unconformity in the photograph?

The interface split between the high point and the low point

What is the difference between felsic and mafic magma and rocks?

Felsic rocks contain more silica than mafic rocks, mafic magmas, lead to effusive volcanism and felsic magmas, to eruptive volcanism, because of their high viscosity, mafic rocks have higher iron and magnesium content and look darker

What is called the layer of debris and unconsolidated materials between the bedrock and the atmosphere?

Sediment

Where is regolith found?

On all terrestrial planets and their moons

What is a difference between pressure and stress for a material?

Pressure represents equal forces in all directions, stress represents possibly different forces in different directions

What is true about metamorphic rocks?

All of igneous, sedimentary, and metamorphic rocks can experience metamorphism

What processes are related to metamorphism?

Diagnesis, foliation, recrystallization

Gneiss is a type of metamorphic rock. What type of metamorphism does it represent?

Intermediate-grade metamorphism (about 310 to 450 degrees Celsius and at moderate pressures)

What is the role of plate tectonics in the rock cycle?

Create sources and sinks, create new igneous rocks,recycles crustal material to the mantle

Iron (Fe) has an atomic number of 26 and an atomic mass of about 55. How many neutrons does it have?

29

Oxygen (O) has an atomic number of 8 and an atomic mass of 16. How many neutrons does it have?

8

Oxygen has an atomic number of 8. How many electrons does it have on its valence shell?

6

Why is noble gas chemically inert?

Because their valence shell is full

Hydrogen, lithium, and sodium are on the left-most column of the periodic table of elements. What type of ion do they form?

Cation

Fluorine and chlorine are in the penultimate column in the periodic table of elements. What type of ions do they form?

Anion

Here is a molecule of water with bonds between oxygen and hydrogen. What type of bond is that?

Covalent bond

Here is sodium chloride (NaCL) in solution. What type of electronic bond is involved?

Transferring of electrons

Here are the molecules of oxygen and the compound of methane. What type of bond is involved?

Sharing of electrons

What state of matter does plasma represent?

Highly compressive material that flows easily, made of electrically charged particles

What is the most common state of material in the universe?

Plasma

What is NOT a process of mineral formation?

Dissolution

What forces minerals to precipitate in an aqueous solution?

Change of temperature, change of chemical composition, evaporation

Stalactites are manifestations of which phenomenon?

Precipitation of calcite from groundwater

What is the first mineral to crystallize in a cooling primordial magma?

Olivine

Many organisms build bones, shells, and body coverings precipitating minerals biologically. What is the most common mineral formed this way?

Calcium Carbonate (CaCO3)

This thin section shows the silica shells of radiolarians, a type of zooplankton, in a chemical sedimentary rock. What is it?

Chert

What type of unconformity is on display in this Telheiro Beach, Portugal outcrop?

Angular unconformity

What is the wavy line between layers B and C in this block diagram?

Disconformity

What is the wavy line between layers G and H in this block diagram?

Angular unconformity

Order the stratigraphic layers A,B,C, and D from older to younger using the principle of superposition

A, B, C, D

Order the strata and geological events using the principles of stratigraphy

A, B, J, C, D, E, F, G, L, K, H, I

Radiometric dating of minerals is based on which physical principles?

The ratio of stable and unstable isotopes is a function of time, the atoms in the mineral must form a closed system, the proportions of stable and unstable isotopes evolve due to radioactive decay

The half-life of carbon-14 (14C) is 5730 years, as it decays to nitrogen-14. How many years does it take to decay half of carbon-14 (14C) atoms in a closed system?

5,730 years

The half-life of carbon-14 (14C) is 5730 years, as it decays to nitrogen-14. How many years does it take to decay 3/4 of carbon-14 (14C) atoms in a closed system?

11,460 years

The half-life of carbon-14 (14C) is 5730 years, as it decays to nitrogen-14. How many years does it take to decay all of carbon-14 (14C) atoms in a closed system?

An infinite time (it never truly happens)

During alpha decay, a type of radioactive decay, 2 neutrons and 2 protons are ejected from the parent isotope as an alpha particle, which also is a helium atom. What statement about the daughter isotope is correct?

The atomic number and the mass number decrease

During beta decay, a neutron in the nucleus of an atom splits into an electron and a proton, producing a beta ray. What statement is correct about the daughter isotope in Beta decay?

The mass number is unchanged, but the atomic number increases by one

Thorium-234 (234Th) decay to protactinium-234 (234Pa) is an example of what type of radioactive decay?

Beta decay

Carbon dating of organic material relies on the radioactive decay of carbon-14 (14C) to nitrogen-14 (14N). What is the source of unstable carbon-14 (14C)?

Interaction of nitrogen-14 (14N) with cosmic particles in the atmosphere

Order the eons of the geologic time scale (chronologically)

Hadean, Archean, Proterozoic, Phanerozoic

What marks the onset of the Phanerozoic eon?

The radiation of complex lifeforms

Order the eras of the phanerozoic (chronologically)

paleozoic, mesozoic, cenozoic

What happened at the Cretaceous-Paleogene boundary, or equivalently, at the end of the Mesozoic?

The extinction of non-avian dinosaurs

What is the current geologic epoch?

Holocene

What is the geologic period of alternating glaciations and interglacial periods?

Pleistocene

When did the Holocene geologic period start?

12,000 years ago

What is the life zone?

The region from 10km underground to 10km above the surface where all live organisms are found

What are the key characteristics of live organisms?

Metabolism, growth, reproduction, and evolution

Select organic compounds from the list

Nucleic acid (e.g., DNA, RNA), Carbohydrates, Lipids, Proteins, Oils

What are autotroph organisms?

Live organisms that derive their own food from inorganic sources, like minerals

What are heterotrophs?

Live organisms that feed from other living organisms or their byproducts

What is the dominant autotrophic process in Earth's biosphere?

Photosynthesis

What chemical reaction is enabled by photosynthesis?

Carbon dioxide combined with water produces sugars and releases oxygen

What are the two mechanisms of chemical growth?

Crystallization and polymerization

What is the energy budget of molecular growth?

Crystallization releases energy and polymerization consumes energy

What is the difference between DNA and RNA?

DNA stores the genetic material; RNA copies it and catalyzes protein synthesis

What are defining characteristics of RNA (ribonucleic acid) biomolecules?

RNA has the capacity to encode genetic material and catalyze chemical reactions

What promotes genetic variations during reproduction?

Genetic recombination in sexual reproduction, random mutations (copies with errors), DNA damage

What property of cellular reproduction or molecular replication enables evolution?

Mutations

What are the characteristics of prokaryotes and eukaryotes?

Eukaryotes are more sophisticated cells and prokaryotes have more rudimentary functions, prokaryotes reproduce asexually and eukaryotes reproduce sexually, all eukaryotes are aerobic cells, using oxygen respiration for metabolism

What is the average lifespan of any single species?

1,000,000 years

What causes speciation?

Barriers to reproduction between different groups of a population, genetic variability and natural selection, genetic drift by geographic isolation

What are the driving factors of natural selection?

Competition with other species, competition with other individuals, environmental changes

What is an important prerequisite in a prebiotic world for the emergence of life?

Availability of pre-biotic molecules, such as amino acids and carbohydrates

What are the possible physical environments where life emerged on Earth?

Hydrothermal systems near the seafloor called black smokers, volcanic zones where heat, minerals, CO2, and water combine, near the ocean surface where atmospheric CO2 and ocean water combine

What is molecular evolution?

The combined result of variability and selection that allowed bio-molecules to perform function

When the solar system formed, where could we find the building blocks of life?

Virtually anywhere in the universe

What is molecular chirality?

Molecules of the same composition that come in mirror-image of each other, the property of molecules to have different functions based on their geometry, the presence of compounds with a left-handed and right-handed version

In the context of the origins of life, what does the citric acid cycle represent?

Molecular self-replication, a reaction series that allows growth, molecules of the citric acid cycle can be used to create bio-building blocks

What property of lipids facilitated the emergence of a membrane surrounding the cell?

Lipid self-assembly

What mechanism enables template-directed synthesis to concentrate and select bio-molecules?

The non-uniform distribution of electrical charges in bio-molecules and mineral surfaces

What presumably explains the chirality of current life processes (left-handed amino acids and right-handed sugars)?

the reproduction of the first cell propagated the handedness of amino acids