Ev Mid Term

Week 1 (1) Terrestrial planets are mainly composed of rock and metals , while the giant planets are made predominantly of volatiles . (2) According to the Big Bang theory, our Universe is expanding . (3) Aside from the Earth, the terrestrial planets are: Mars, Mercury, and Venus (4) Explain the phrase “We are all made of Stardust”. Means that the atoms in our bodies and the elements on Earth originated in the cores of stars through nuclear fusion and were later scattered into space, eventually forming us and our planet. (5) What is the difference between nuclear fusion and nuclear fission? Nuclear fusion combines light nuclei to release energy, as in the sun. Nuclear fission splits heavy nuclei to release energy, as in nuclear reactors. (6) Regarding the formation of a planet, what is accretion? Accretion is the process of small particles and materials in space coming together and accumulating to form a planet. (7) Explain how xenoliths can provide evidence about the Earth’s internal structure/composition. Xenoliths are rock fragments brought to the surface by volcanoes, offering direct samples of the Earth's mantle to study its composition and properties. (8) What other evidence can be used to determine the Earth’s internal structure/composition. Other evidence for Earth's internal structure includes seismic studies, gravity/magnetic surveys, and computer modeling. (9) What have seismic waves taught us about the interior of our planet? Seismic waves have revealed the Earth's layered structure: a solid inner core, a liquid outer core, a solid mantle, and a solid crust. They also help determine layer boundaries and properties, like the Moho and Gutenberg Discontinuity depths Week 2 (10) The densest layer of the Earth is the inner core (11) Compared to oceanic crust, continental crust is thicker (12) The Moho lies at greater depth under oceans than under continents

(13) From left to right, correctly label each section of this slice of the Earth by choosing from the options below. Note that 1 starts at the surface of the Earth and 6 ends at the centre of the Earth crust, upper mantle, transition zone, lower mantle, liquid outer core, solid inner core (14) The lithosphere is composed of the crust and the uppermost part of the mantle. (15) The lithosphere lies directly above the asthenosphere. (16) What are the main differences between continental and oceanic crust? Continental crust is thicker, less dense, and composed of granitic rocks, while oceanic crust is thinner, denser, and made of basaltic rocks. Continental crust is older, with diverse topography, and experiences tectonic activity. Oceanic crust is younger, primarily forms ocean basins, and has higher heat flow. (17) What are the main differences between the lithosphere and asthenosphere? The lithosphere is the rigid, solid outer layer of the Earth, while the asthenosphere is a semi- fluid layer beneath it that allows for the movement of tectonic plates. (18) Which layer of the Earth is thought to be completely molten? Why? The outer core is believed to be completely molten because it lacks S-waves, which can't pass through liquids, and it refracts P-waves in a manner consistent with a liquid state. (19) Why does basalt have a memory of the Earth’s magnetic field from the time it crystallises? Basalt retains a memory of the Earth's past magnetic field because its magnetic minerals align with the Earth's magnetic field when it solidifies. (20) What is a magnetic anomaly? A magnetic anomaly is a variation in the Earth's magnetic field at a specific location, either stronger or weaker than expected, often indicating differences in subsurface magnetic properties. (21) A body of rock starts at location A in the graph below. The rock, over a period, moves to location B and begins to melt. This is an example of melting due to decompression (22) The geotherm is the rate of change of temperature with depth in the Earth’s interior (23) Calculate the pressure at the bottom of a 5 km thick sandstone formation. The density of sandstone is 2.7 g/cm 3 . Give your answer in Pa and in kbar Pressure (P) = Density (ρ) × Gravity (g) × Height (h) where:  Density (ρ) = 2.7 g/cm³ = 2700 kg/m³ (converting grams per cubic centimeter to kilograms per cubic meter)

o Geothermal gradient for the mantle (ΔT/Δd) = 10°C/km o Depth within the crust (d) = 35 km (since the crust is 35 km thick) o Depth within the mantle (d) = 60 km - 35 km = 25 km (since we've already accounted for the crust) We'll calculate the temperature in two steps: Step 1: Calculate the temperature at the base of the crust (35 km): T = T + (ΔT/Δd) × d T ₁ ₀ ₁ = T + (35°C/km) × 35 km T = T + 1225°C ₀ ₁ ₀ Step 2: Calculate the temperature within the mantle (25 km into the mantle): T = T + ₂ ₁ (ΔT/Δd for the mantle) × d (depth within the mantle) T = (T + 1225°C) + (10°C/km) × 25 ₂ ₀ km T = T + 1225°C + 250°C T = T + 1475°C ₂ ₀ ₂ ₀ So, the temperature at 25 km depth is T + 875°C, and the temperature at 60 km depth is T + ₀ ₀ 1475°C, where T is the initial surface temperature. ₀ Minerals (1) Which of the following are good conductors due to the ability of the electrons in the atoms to move around freely? Native minerals (2) What is an isotope? An isotope is a variant of an element with the same number of protons but a different number of neutrons in its atomic nucleus, resulting in variations in atomic mass. (3) Minerals are all naturally occurring solid substances with a definable chemical composition. They must also possess a fixed crystalline structure (spatial arrangement of atoms and ions) (4) Why is volcanic glass NOT a mineral? It has no defined crystal structure. (5) Crystals that exhibit well-formed faces are referred to as euhedral. (6) What tools do we use to identify minerals in hand specimen? Tools for identifying minerals in hand specimens include hand lens, streak plate, hardness test (Mohs scale), cleavage/fracture observation, acid test, magnetism test, taste/smell assessment, specific gravity measurement, UV light examination, and chemical tests. (7) Why is mineral colour an unreliable mineral property? Mineral color is unreliable for identification because it can vary due to impurities, variations in mineral composition, lighting conditions, surface alterations, metamorphism, and subjectivity. Other mineral properties like hardness, streak, and cleavage are more reliable for identification. (8) Crystal form or crystal shape is a useful mineral characteristic that can be used to identify minerals, but it is unfortunately rarely observed. What is the reason for this?

Crystal form or shape is rarely observed in mineral identification because many minerals do not naturally develop distinct crystal shapes due to factors like environmental conditions, impurities, small crystal size, metamorphism, fragmentation, and external factors. Other properties are more commonly used for identification. (9) What are cleavage and fracture? How are these physical properties similar and/or different? Cleavage is the property where minerals break along specific, smooth planes, while fracture is the property where minerals break irregularly, producing rough surfaces. Both properties are used for mineral identification. (10)Why does the pressure increase as we go deeper into the Earth? Pressure rises deeper into the Earth due to the weight of overlying rocks and materials, causing greater compression. (11)Why does the temperature increase as we go deeper into the Earth? Temperature rises with depth due to radioactive heat generation and the geothermal gradient, where heat from the Earth's interior flows outward. (12)What is a geotherm? A geotherm is a profile showing how temperature changes with depth within the Earth's interior, providing insights into its thermal structure. (13)What is a geothermal gradient?  how to calculate it The geothermal gradient is the rate of temperature increase with depth (typically in °C/km). It's calculated as (T₂ - T₁) / (d₂ - d₁), where T represents temperature, and d represents depth at two points. (14) Rock-forming silicate minerals  main ones she wants us to learn. - Feldspar: plagioclase and K-feldspar - Quartz - Mica: biotite and muscovite - Amphibole - Pyroxene - Olivine - Garnet (15) Question on how the mineral properties are controlled by the structure of the mineral . Mineral properties, including cleavage, hardness, color, and more, are directly determined by the atomic structure of the mineral. The arrangement of atoms or ions within a mineral's crystal lattice dictates its observable characteristics. Week 3 (16) In which type of silicates are the greatest proportion of oxygen atoms shared by pairs of

Week 4 (28)What is a super-volcano? A super-volcano is a volcano capable of extremely large eruptions. (29)How will a super volcano eruption effects its immediate surroundings and the Earth: A super-volcano eruption can have catastrophic effects locally and globally, including the formation of large calderas, the release of massive ash and gases, regional devastation, climate impacts, and potential disruptions to ecosystems. (30)Which minerals would you expect in a rock that formed at 1000-1100°C? At 1000-1100°C, you would expect minerals like olivine, pyroxene, and plagioclase in a rock. (31)Would be the viscosity of a magma at a temperature of 1000-1100°C be high or low? The viscosity of magma at 1000-1100°C would be low. (32)A rock comprises olivine, pyroxene, and Na-rich plagioclase. Is this possible? Explain Yes, a rock can comprise olivine, pyroxene, and Na-rich plagioclase, indicating a mafic or ultramafic composition. (33)A rock comprises quartz, biotite, K-feldspar, and Na-rich plagioclase. Is this possible? Explain your answer. Yes, a rock can comprise quartz, biotite, K-feldspar, and Na-rich plagioclase, indicating a granitic or granodioritic composition. (34)Describe and explain the relationship between colour index, mineral content, and magma chemistry (SiO 2 content). Use the Bowen’s reaction series diagram to help. Color index, mineral content, and magma chemistry are related. A high color index is associated with mafic rocks, while a low color index is associated with felsic rocks. (35)What is a tuff? How does a tuff form? A tuff is formed from the consolidation of volcanic ash. (36)The Undara lava tube (see picture below) in North Queensland is one of the longest basaltic lava flows in the world (ca. 160 km). The amount of lava that was produced is ca. 23 km 3 . The lava flow is ca. 190,000 years old. What do you think is the cause of this volcanism? Explain your answer. The Undara lava tube volcanism in North Queensland is caused by a volcanic hotspot or mantle plume beneath the region, leading to basaltic lava eruptions and the formation of extensive lava flows and tubes. (37) Seafloor spreading is most likely to occur at divergent boundaries (38) Compared to typical oceanic lithosphere, the thickness of continental lithosphere is higher

(39) At a subduction zone, the overriding plate may be composed of either oceanic or continental lithosphere. (40) At a subduction zone, the downgoing (subducting) plate is usually composed of oceanic lithosphere (41) List and briefly describe the three different plate boundary types. Give an example of where on Earth you could find each type of plate boundary. Divergent Boundaries : Plates move apart, creating new crust (e.g., Mid-Atlantic Ridge) Convergent Boundaries : Plates move toward each other, leading to subduction or mountain formation (e.g., Andes). Transform Boundaries : Plates slide past each other horizontally, causing earthquakes (e.g., San Andreas Fault) (42)Continental crust is far less likely to subduct than oceanic crust. Why is that? Continental crust resists subduction due to its lower density compared to oceanic crust. (43)What is the name of the plate that comprises the Hawaii Islands? The Hawaii Islands are on the Pacific Plate. (44)In which direction is this plate moving? Explain your answer. The Pacific Plate is moving northwest due to the formation of new oceanic crust. (45)stages of the Wilson cycle: The Wilson Cycle involves continental rifting, ocean formation, subduction, and collision in a geological cycle. (46)Explain why the oldest ocean floor rocks are ca. 150 million years old whereas continental rocks can be older than 3 billion years. The age difference results from plate tectonics: Oceanic crust is continually created and recycled due to seafloor spreading and subduction, limiting its age to about 150 million years. In contrast, continental crust is less dense and resists subduction, allowing rocks to accumulate and persist for over 3 billion years. (47) Mid-ocean ridges tend to be roughly symmetrical about the ridge axis (48) Beneath a blanket of sediments, oceanic crust is primarily composed of basalt (49) Seafloor spreading is driven by volcanic activity along mid-ocean ridges (50)What arguments did Alfred Wegener use to propose continental drift? Alfred Wegener used evidence such as the fit of continents, similar fossils on separated

 The fine-grained nature of chert does not necessarily indicate fast cooling. Chert is typically composed of microcrystalline quartz and forms through chemical processes.  Well-rounded, very poorly sorted quartz crystals in sandstone are contradictory descriptions. Well-rounded clasts suggest good sorting.  A breccia consists of angular to subangular boulder-sized clasts, not well-rounded ones. (63)Indicate for the following sedimentary rocks whether they are chemical (inorganic), biochemical, clastic/detrital. Give a brief explanation.  Sandstone: Clastic/detrital (composed of sand-sized particles).  Fossiliferous limestone: Biochemical (contains fossils made of calcium carbonate).  Shale: Clastic/detrital (composed of fine clay and silt-sized particles).  Chert: Chemical (usually forms from the precipitation of silica).  Rock salt: Chemical (forms through the evaporation of saline water).  Claystone: Clastic/detrital (composed of clay-sized particles).  Conglomerate: Clastic/detrital (contains rounded pebbles). (64)Name four mineral that you can commonly find in sedimentary rocks: Four common minerals in sedimentary rocks are quartz, feldspar, calcite, and clay minerals. (65)Name two minerals that precipitate when salt water evaporates: Two minerals that precipitate when salt water evaporates are halite (rock salt) and gypsum. (66)Conglometate is a rock comprising rounded pebbles. Why are the pebbles rounded? Conglomerate rocks often contain rounded pebbles because the pebbles have undergone abrasion and wear during transportation by water, rounding off their edges and corners. This process is called mechanical weathering. Crossbedding - Cross laminations that form at an angle to the bed that contains them. - Ripples (small) and dunes (large) form laminations in the direction of the prevailing current - Subsequent ripples crosscut the earlier laminations. - Fluvial, marine or aeolian Week 6

(67) A protolith may belong to any of the three primary rock types (68) The application of differential stress during metamorphism causes elongated crystals to align parallel with each other. When this happens, the rock develops foliation . (69) Slaty cleavage, schistosity, and compositional banding are all examples of foliation (70) Marble and quartzite are non-foliated metamorphic rocks because both are dominated by minerals that produce equant grains (71) The blueschist facies form under which of these conditions: high pressure but relatively low temperature (72)What are the main differences between contact and regional metamorphism? Contact metamorphism occurs when rocks are subjected to high temperatures and low pressures, typically near an igneous intrusion or along fault zones. Regional metamorphism, on the other hand, occurs under high pressures and temperatures over large regions due to tectonic forces. (73)Explain why the rocks are different despite the fact that they formed at the same pressure and temperature. The rocks can be different despite forming at the same pressure and temperature due to variations in their protolith (original rock) compositions and mineral content. Different protoliths can lead to different mineral assemblages and textures during metamorphism. (74)What metamorphic facies would most commonly be associated with a subduction zone and why? Blueschist facies is commonly associated with subduction zones due to its unique combination of high pressure and low temperature conditions. (75)What are three metamorphic rocks that form when mafic crust is subducted. Three metamorphic rocks that can form when mafic crust is subducted are blueschist, eclogite, and garnet amphibolite. (76)Name two protolith rocks and a metamorphic rock that can form from them.  Protolith: Shale Metamorphic rock: Slate  Protolith: Limestone Metamorphic rock: Marble (77) spreading peanut butter on bread is an application of shear stress (78) Name three change that occur during metamorphism . Three changes that occur during metamorphism are recrystallization, mineral reorientation, and the growth of new minerals. (79) Porphyroblasts = large crystal surrounded by finegrained matrix in a metamorphic rock (similar to a phenocryst in igneous rocks)  for metamorphic rocks only