Geology 1610 Paul Hudak Exam 1 (Chapters 1-4)

What processes must take place to transform rocks into sediment? (Ch. 3)

It must be exposed at surface so in many cases uplift and removal of overlying sediments is required. Then chemical and/or physical weathering can take place, which reduces the rock to smaller loose fragments. These fragments are sediments that can be eroded and then transported by a variety of maechanisms.

Calcite

Made of calcium carbonate; white to clear; scratched with a knife; reacts to hydrochloric acid; component of most seashells.

Intrusive Igneous Bodies (Ch. 3)

Magma intrudes into country rock by pushing it aside or melting through it. Intrusive igneous bodies tend to be either irregular (stocks and batholiths), tabular (dykes and sills), or pipe-like. Batholiths have exposed areas of greater than 100 km 2 , while stocks are smaller. Sills are parallel to existing layering in the country rock, while dykes cut across layering. A pluton that intruded into cold rock it is likely to have a chilled margin.

Magma (Ch. 3)

Magma is molten rock, it forms from partial melting of existing rock. Magmas range in composition from ultramafic to felsic. Mafic rocks are rich in iron, magnesium, and calcium and have around 50% silica. Felsic rocks are rich in silica (~75%) and have lower levels of iron, magnesium, and calcium and higher levels of sodium and potassium than mafic rocks.

How does mantle convection contribute to plate tectonics? (Ch. 1)

Mantle convection creates the traction that can force plates to move around on the surface.

Quartz

Mineral made of silicon dioxide; varieties based on color include amethyst (purple), smoky (grey), rose (pink), and citrine (yellow-green); glassy luster; hardness of 7

Mineral Groups (Ch. 2)*

Minerals are grouped according to the anion part of their formula; common groups: oxides, sulphides, sulphates, halides, carbonates, phosphates, silicates, and native minerals.

Minerals (Ch. 1)

Minerals are naturally occurring, specific combinations of elements that have particular three-dimensional structures.

Formation of Minerals (Ch. 2)

Most minerals in the crust form from the cooling and crystallization of magma. Some form from hot water solutions, during metamorphism or weathering, or through organic processes.

Mineral groups and examples: (Ch. 2)*

Oxides: hematite, magnetite, water ice Sulphides: galena, pyrite Carbonates: calcite, Silicates: biotite, orthoclase, quartz, olivine, gypsum Native: graphite Halide: fluorite

How would some familiarity with biology be helpful to a geologist? (Ch. 1)

Paleontology is an important aspect of geology and requires an understanding of biology, including evolution, the physiology of animals and plants and ecological relationships.

How are the silica tetrahedra structured differently in pyroxene and amphibole? (Ch. 2)

Pyroxene is made up of single chains of tetrahedra while amphibole is made up of double chains.

What are the processes that lead to the formation of a metamorphic rock? (Ch. 3)

Rock is buried within the crust and heated because of the geothermal gradient. At temperatures over 200˚C some of the existing minerals may become unstable and will be converted to new minerals, or recrystallized into larger crystals.

Sedimentary Rocks

Rocks forming from deposits of pre-existing rocks or pieces of once-living organisms; often have distinctive layering; are classified into: Clastic, Biologic, and Chemical.

Metamorphic rocks

Rocks forming when high temperatures and pressure act on a rock to alter its physical and chemical properties

Igneous rocks

Rocks forming when hot, molten rock (magma) crystallizes and solidifies.

What processes normally take place in the transformation of sediments to sedimentary rock? (Ch. 3)

Sediments are buried beneath other sediments where, because of the increased pressure, they become compacted and dewatered. With additional burial they are warmed to the point where cementing minerals can form between the grains (less than 200˚C).

What mineral group makes up the vast majority of Earth's crust? (Ch. 2)*

Silicate

Potassium feldspar

Silicate mineral containing considerable amount of potassium; typically pink-salmon to white in color; hardness of 6

Plagioclase feldspar

Silicate mineral containing considerable sodium or calcium; generally white to gray; glassy luster

Olivine

Silicate mineral containing iron and magnesium; green and glassy; forms at high temperatures; common in basalt and ultramafic rocks

Micas

Silicate minerals forming flat, sheet-like crystals that peel apart; varieties include biotite (black or brown) and muscovite (light-colored); hardness of approximately 2.5

Amphiboles

Silicate minerals forming prism or needle-like crystals; generally dark-colored

Talc

Softest known mineral, scratched with fingernail; greasy feel; waxy luster; associated with metamorphic rocks

Bonding (Ch. 2)

The main types of bonding in minerals are ionic bonding (electrons transferred) and covalent bonding (electrons shared). Some minerals have metallic bonding or other forms of weak bonding.

What are the names and compositions of the two end-members of the plagioclase series? (Ch. 2)

The two end-members of the plagioclase series are Albite (NaAlSi 3 O 8) and Anorthite (CaAl 2 Si 2 O 8)

Magma Formation (Ch. 3)

The two processes are decompression melting and flux melting.

Classification of Igneous Rocks (Ch. 3)

They are classified based on their mineral composition and texture. (1)Felsic igneous rocks have less than 20% ferromagnesian silicates (amphibole and/or biotite) plus varying amounts of quartz and both potassium and plagioclase feldspars. (2)Mafic igneous rocks have more than 50% ferromagnesian silicates (primarily pyroxene) plus plagioclase feldspar. (3)Most intrusive igneous rocks are phaneritic (crystals are visible to the naked eye). If there were two stages of cooling (slow then fast), the texture may be porphyritic (large crystals in a matrix of smaller crystals). If water was present during cooling, the texture may be pegmatitic (very large crystals).

What process leads to convection in the mantle? (Ch. 1)

Transfer of heat from the core to the mantle leads to heating of lower mantle rock. When heated, the rock expands and its density is reduced. Because the mantle is plastic, this lower-density material tends to rise toward the surface, and cooler denser mantle material moves in to take its place.

Foliated Metamorphic Rocks

Type of metamorphic rock formed as pressure causes platy or elongated minerals to become aligned

Chemical Sedimentary Rock

Type of sedimentary rock formed by chemical precipitation that begins when water dissolves minerals in rock

Biologic Sedimentary Rock

Type of sedimentary rock formed when living organisms die, pile up, compress, and cement together

Clastic Sedimentary Rock

Type of sedimentary rock made of pieces (clasts) of pre-existing rocks loosened by weathering

What is a mineral lattice? (Ch. 2)*

a specific "repeating three-dimensional structure/lattice" which is the way in which the atoms are arranged. The nature of the lattices and the type of bonding within them have important implications for mineral properties.

What is a hypothesis? (Ch. 1)*

a tentative explanation that could explain the observations that have been made; and then the formulation and testing (by experimentation) of one or more predictions that follow from that hypothesis.

What chemical feature is used in the classification of minerals into groups? (Ch. 2)

anion or anion group.

Silicate Minerals (Ch. 2)

are the most important minerals in Earth's crust. They all include silica tetrahedra (four oxygens surrounding a single silicon atom) arranged in different structures (chains, sheets, etc.). Some silicate minerals include iron or magnesium and are called ferromagnesian silicates.

Why is colour not necessarily a useful guide to mineral identification? (Ch. 2)*

because many minerals have a wide range of colours due to differing impurities.

What allows magnesium to substitute freely for iron in olivine? (Ch. 2)

because they have similar charges (+2) and similar ionic radii.

What is a metamorphic rock? (Ch. 3)*

formed by alteration (due to heat, pressure, and/or chemical action) of a pre-existing igneous or sedimentary rock

Mineral Properties (Ch. 2)*

hardness, cleavage/fracture, density, lustre, colour, and streak colour.

The three types of rocks are (Ch. 3)

igneous, formed from magma; sedimentary, formed from fragments of other rocks or precipitations from solution; metamorphic, formed when existing rocks are altered by heat, pressure, and/or chemical action.

What are the two most common chemical bonds in minerals? (Ch. 2)*

ionic bonds and covalent bonds

What is the main component of Earth's core? (Ch. 1)

iron (Fe)

Name three intrusive igneous bodies.(Ch. 3) *

irregular (stocks and batholiths) tabular (dykes and sills) pipe-like laccolith sill-like

Rocks (Ch. 3)*

is a consolidated (hard and strong) mixture of the same or different minerals; can form though igneous, sedimentary, or metamorphic processes.

Geological Time Earth (Ch. 1)*

is approximately 4,570,000,000 years old = 4.57 billion= 4.57 Ga or 4,570 Ma.

What is a mineral? (Ch. 1)*

is formed naturally by geological processes. A mineral is a homogeneous solid that can be made of single native element or more usually a compound. Minerals make up Earth's rocks and sands, and are an important component of soils.

What is magma? (Ch. 1)*

molten rock; originates deep within the Earth, near active plate boundaries or hot spots. When it rises to the surface is called lava. Igneous rocks are classified into two groups depending upon where the molten rock solidifies: Extrusive or Intrusive.

What do all silicate minerals have in common? (Ch. 2)*

silica tetrahedra (four oxygens surrounding a single silicon atom)

The Rock Cycle (Ch. 3)*

the processes that contribute to cycling of rock material among these three types. The rock cycle is driven by Earth's internal heat, and by processes happening at the surface, which are driven by solar energy.

What Is Geology? (Ch. 1)

the study of Earth; an integrated science that involves the application of many of the other sciences, but geologists also have to consider geological time because most of the geological features that we see today formed thousands, millions, or billions of years ago.

Why are helium and neon (and the other noble gases) non-reactive? (Ch. 2)

they have complete outer shells and therefore no tendency to form ionic bonds.

What are the major components (parts) of Earth's internal structure? (Ch. 1)*

three main layers: the core, the mantle and the crust.

List three ways in which geologists can contribute to society. (Ch. 1)

(1) provide information to reduce the risk of harm from hazards such as earthquakes, volcanoes, and slope failures; (2) they play a critical role in the discovery of important resources; (3) they contribute to our understanding of life and its evolution through paleontological studies; (4) they play a leading role in the investigation of climate change, past and present and its implications.

Two ways in which batholiths (or stocks) intrude into existing rock. (Ch. 3)

(a) melting through the country rock, or (b) causing the country rock to break and fall into the magma (stoping), or (c) pushing the country rock aside.

What is the maximum value on Moh's hardness scale? (Ch. 2)*

10

Dinosaurs first appear in the geological record in rocks from about 215 Ma and then became extinct 65 Ma. For what proportion (%) of geological time did dinosaurs exist? (Ch. 1)

215-65=150 Ma. age of the Earth is 4570 Ma, this represents 150/4,570=0.033=3.3% of geological time

Lithification

8. Conversion of loose sediment into solid sedimentary rock; includes compaction and cementation

What is the difference between a batholith and a stock? (Ch. 3)

A batholith has an exposed area of greater than 100 km 2; a stock has an exposed area less than that.

With respect to tabular intrusive bodies, what is the difference between a concordant body and a discordant body? (Ch. 3)

A concordant body (a sill) is parallel to any pre-existing layering (bedding or foliation) in the country rock is. A discordant body (a dyke) cuts across any pre-existing layering or is situated at any angle in country rock that has no layering (e.g., granite).

In what way is a mineral different from a rock? (Ch. 1)*

A mineral has a specific chemical composition and lattice structure. Rocks are made out of minerals, and most rocks contain several different types of minerals.

Why does a dyke commonly have a fine-grained margin? (Ch. 3)

A rock has to crack in order for a dyke to intrude into it, and it has to be cool to crack. When the hot magma intrudes into the cold country rock its margins cool quickly (forming small crystals), while its centre cools more slowly (forming larger crystals).

What is the electrical charge on an anion? A cation? (Ch. 2)

An anion has a negative charge A cation has a positive charge.

Electrons, Protons, Neutrons, and Atoms (Ch. 2)

An atom is made up of protons and neutrons in the nucleus and electrons arranged in energy shells around the nucleus. The first shell holds two electrons, and outer shells hold more, but atoms strive to have eight electrons in their outermost shell (or two for H and He). They either gain or lose electrons (or share) to achieve this, and in so doing become either cations (if they lose electrons) or anions (if they gain them).

basalt

An extrusive rock with 40% Ca-rich plagioclase and 60% pyroxene

granite

An intrusive rock with 25% quartz, 20% orthoclase, 50% feldspar, and minor amounts of biotite

diorite

An intrusive rock with 65% plagioclase, 25% amphibole, and 10% pyroxene

What is the net charge on an unbonded silica tetrahedron? (Ch. 2)

An unbonded silica tetrahedron has one Si ion (+4 charge) and 4 oxygens (-2 charge each) so the overall charge is 4 - 8 = -4 for SiO 4 ^-4

Crystallization of Magma (Ch. 3)

As a body of magma starts to cool, the first process to take place is the polymerization of silica tetrahedra into chains. This increases the magma's viscosity (makes it thicker) and because felsic magmas have more silica than mafic magmas, they tend to be more viscous. The Bowen reaction series allows us to predict the order of crystallization of magma as it cools. Magma can be modified by fractional crystallization (separation of early-forming crystals) and by incorporation of material from the surrounding rocks by partial melting.

What is the significance of the term reaction in the name of the Bowen reaction series? (Ch. 3)

As the temperature decreases minerals that formed early (e.g., olivine) may react with the remaining magma to form new minerals (e.g., pyroxene).

If a typical rate for the accumulation of sediments is 1 mm/year, what thickness (metres) of sedimentary rock could accumulate over a period of 30 million years? (Ch. 1)

At 1 mm/y: 30,000,000 mm= 30,000 m = 30km would accumulate over 30 million years. Few sequences of sedimentary rock are even close to that thickness because most sediments accumulate at much lower rates, more like 0.1 mm/y.

5 characteristics required of all minerals

Be naturally-occurring; Be Inorganic (not living, or from plants or animals); Be solid; Have a typical ordered internal structure; Have a definite chemical composition.

Why is biotite called a ferromagnesian mineral, while muscovite is not? (Ch. 2)

Biotite includes iron and/or magnesium in its formula, while muscovite does not.

Why is it common for plagioclase crystals to be zoned from relatively calcium-rich in the middle to more sodium-rich on the outside? (Ch. 3)

Calcium-rich plagioclase forms early on in the cooling process of a magma, but as the temperature drops, a more sodium-rich variety forms around the existing crystals.

What is the electrical charge on a proton? A neutron? An electron? What are their relative masses? (Ch. 2)

Charges: proton: +1, neutron: 0, electron: -1, Masses: proton: 1, neutron: 1, electron: almost 0.

What is the difference between mineral cleavage and fracture? (Ch. 2)*

Cleavage is what we see when a mineral breaks along a specific plane/planes, while fracture is an irregular break.

List and briefly define four mineral properties. (Ch. 2)*

Colour: some minerals have particularly distinctive colours that make good diagnostic properties, many do not; Streak: color of the mineral in powdered form shows its "true" colour. Hardness: a measure of the mineral's resistance to scratching (Mohs scale) Lustre: indicate how much light reflects off the surface of a mineral, and the degree to which it penetrates into the interior.

Fluorite

Common colors include purple, green, yellow, and blue; visible under ultraviolet light; hardness of 4

Why is compositional layering a common feature of mafic plutons but not of felsic plutons? (Ch. 3)

Compositional layering forms when early-crystallizing mineral sink toward the bottom of a magma chamber. This can only happen in non-viscous magma, and mafic magma is typically much less viscous than felsic magma.

Fundamentals of Plate Tectonics (Ch. 1)

Convection currents move through Earth's mantle because the mantle is being heated from below by the hot core. Those convection currents cause the movement of tectonic plates (which are composed of the crust and the uppermost rigid mantle). Plates are formed at divergent boundaries and consumed (subducted) at convergent boundaries. Many important geological processes take place at plateboundaries.

What drives tectonic plates? (Ch. 1)*

Convection in the mantle is the driving force for the movement of tectonic plates. (Heat is continuously flowing outward from Earth's core to the mantle causes convection in the mantle).

What must happen within a magma chamber for fractional crystallization to take place? (Ch. 3)

Early-forming minerals, which are typically quite dense (e.g., olivine) may sink to the bottom of the magma chamber (if the magma is not too viscous) and thus become separated from the rest of the magma, resulting in a change to the composition of the remaining magma (it becomes more felsic).

What is the difference in the role of electrons in an ionic bond compared to a covalent bond? (Ch. 2)

Electrons are transferred from one atom to another to form an ionic bond. Electrons are shared between atoms to form a covalent bond.

Which of the following minerals is an oxide: PbS, Fe2O3, NaCl, or CuFeS2? (Ch. 2)*

Fe2O3 (Ferric oxide)

Why Study Earth? (Ch. 1)

Geologists study Earth out of curiosity and for understanding the evolution of life on Earth; searching for resources; understanding risks from geological events such as earthquakes, volcanoes, and slope failures; and documenting past environmental and climate changes so that we can understand how human activities are affecting Earth.

What do Geologists Do? (Ch. 1)

Geologists work in the resource industries and in efforts to protect our resources and the environment in general. They are ensuring that risks from geological events (e.g., earthquakes) are minimized and that the public understands what the risks are. They engaged in fundamental research about Earth and in teaching.

In what way is geology different from the other sciences, such as chemistry and physics? (Ch. 1)

Geology involves integration of various different sciences (chemistry, physics, and biology for example), but also requires an understanding of the importance of billions of years of geological time.

You have an unknown mineral that can scratch glass but cannot scratch a porcelain streak plate. What is its approximate hardness? (Ch. 2)*

Glass has a Mohs hardness of about 5.5 while porcelain is close to 6.5. The mineral is between these two, so it must be close to 6.

Describe the lattice structure and elemental composition of the mineral halite. (Ch. 1)

Halite is composed of sodium(Na) and chlorine(Cl) with the Na+ and Cl-ions alternating with one another in all three directions within a cubic structure.

What are some of the processes that take place at a divergent plate boundary? (Ch. 1)

Hot mantle rock moving toward the surface partially melts because the pressure is reduced. The magma produced moves upward into cracks in the crust and is extruded onto the sea floor.

Explain how the need for an atom's outer shell to be filled with electrons contributes to bonding. (Ch. 2)

If the outer shell is not quite full, the atom may gain electrons to fill them and become an anion (negative charge). If the outer shell has only a few electrons, it may lose them and become a cation (positive charge). Cations and anions attract each other to form molecules with ionic bonding.

Explain the difference between aphanitic and phaneritic textures. (Ch. 3)

If the texture is aphanitic the crystals are too small to see without a microscope. In rocks with phaneritic textures the minerals are large enough to see and distinguish from each other with the naked eye. The dividing line is somewhere between 0.1 and 1 mm, depending on the minerals.

Intrusive Igneous Rock

Igneous rock formed when magma cools inside Earth; visible crystals

Extrusive Igneous Rock

Igneous rock produced when lava cools at or near Earth's surface; fine-grained, glassy, or vesicular texture

Mafic

Igneous rocks with abundant dark-colored minerals rich in magnesium or iron

Felsic

Igneous rocks with abundant light-colored minerals

What are the three rock groups? (Ch. 1)*

Igneous, Sedimentary, and Metamorphic (classify on how they were formed)

Explain the difference between porphyritic and pegmatitic textures. (Ch. 3)

In porphyritic rocks there are two distinct crystal sizes that are indicative of two stages of cooling (slow then fast). The fine material can range from glass to several mm, as long as the coarse crystals are distinctively larger. In pegmatitic rocks the crystals are consistently coarser than 1 cm, and can be much larger. Pegmatites form the slow cooling of water-rich magmas.

Why does quartz have no additional cations (other than Si +4 )? (Ch. 2)

In quartz each silica tetrahedron is bonded to four other tetrahedra, and since oxygens are shared at each bond the overall ratio is silicon (+4) to two oxygens (2 x -2 = -4), which is balanced.