Minerals and Ore (?)

Definition and Examples:

• Minerals — Natural, Inorganic, Solid, Possess an Orderly Internal Structure of Atoms, Have a Definite Chemical Composition

• Rock — Any naturally occurring solid mass of mineral or mineral-like matter (aggregates of minerals).

• Elements — Basic building blocks of minerals, over 100 are known.

• Concept of Ore

Diagnostic Properties of Minerals:

• Habit — Common crystal shape.

• Luster — Appearance in reflected light.

• Color

• Streak — Color of mineral in powdered form.

• Hardness — Ability to resist scratching or abrasion.

• Cleavage — Tendency to break along planes of weak bonding.

• Fracture — Random pattern of breakage.

• Specific Gravity — Mineral density

• Tenacity — Resistance to cutting, breaking, bending, and deformation.

Moh’s Hardness Scale:

Bowen’s Reaction Series — The order of crystal formation from magma as cooling occurs (discontinuous and continuous series).

• Temperature at which minerals change from solid to liquid.

  

Rock-Forming Silicates — Contain the silicon-oxygen tetrahedron.

• Four oxygen atoms surrounding a much smaller silicon atom.

• Combines with other atoms to form the various silicate structures.

• Grouped based upon tetrahedral arrangement:

  • Olivine — Independent tetrahedral

  • Pyroxene Group — Tetrahedra are arranged in chains.

  • Amphibole Group — Tetrahedra are arranged in double chains.

  • Micas — Tetrahedra are arranged in sheets (biotite; dark & muscovite; light)

  • Feldspars & Quartz — Three-dimensional network of tetrahedra.

Ore — A mineral or aggregate of minerals that contains one or more valuable constituents (metals, gemstones, or other materials) that can be extracted profitably.

Characteristics of Ore:

• A material must have sufficient value to justify extraction and processing costs.

• Ore must have a higher concentration of the desired mineral compared to the Earth's crust's average abundance (known as the "cutoff grade").

• Ore deposits form under specific geological conditions and can be associated with igneous, sedimentary, or metamorphic environments.

Types of Ore:

• Metallic Ores — Contain metals that can be extracted.

  • e.g., Gold, silver, and platinum from precious metal ores.

  • e.g., Iron, aluminum, and copper from industrial metal ores.

• Non-Metallic Ores — Contain minerals of economic value but not metals. Examples:

  • e.g., Phosphates for fertilizers and halite (rock salt) for industrial and domestic use.

Formation of Ore Deposits:

• Magmatic Processes — Crystallization of minerals from molten magma (e.g., chromite deposits)

• Hydrothermal Processes — Mineral-rich fluids deposit minerals in cracks and fissures (e.g., vein gold).

• Sedimentary Processes — Minerals are concentrated through sedimentary sorting (e.g., placer gold deposits).

• Metamorphic Processes — High temperature and pressure cause mineral reorganization (e.g., graphite ore).

Igneous/Metamorphic/Sedimentary Rocks.

Weathering (5)

1. What the different types of physical weathering? Provide examples.

Physical (mechanical) weathering — The process of breaking down rocks into smaller fragments without changing their chemical composition.

Frost Wedging (Freeze-Thaw) Weathering — Water enters crack in rocks, freezes, and expands by about 9%. The expansion exerts pressure on the rock, causing it to crack and eventually break apart.

• e.g., common in cold climates; creates sharp, angular fragments and talus slopes at the base of cliffs.

Thermal Expansion & Contraction — Rocks expand when heated and contract when cooled; repeated cycles of expansion and contraction weaken the rock, causing it to fracture.

• e.g., occurs in deserts (temperature extremes); leads to the exfoliation of rock surfaces (e.g., peeling layers in granite domes).

Exfoliation (Unloading/Pressure Release) Weathering — Deeply buried rocks are under immense pressure from overlying materials; when the overlying material is eroded away, the pressure is released, causing the rock to expand and crack, often in sheets.

• e.g., found in granite formations like Yosemite National Park, where large, dome-like structures form due to exfoliation.

Salt Crystallization — Saline water enters rock pores or cracks; when the water evaporates, salt crystals grow, exerting pressure on the surrounding rock and causing it to break apart.

• e.g., common in coastal or arid regions; forms honeycomb weathering patterns in sandstone cliffs.

Biological (Root Wedging) Weathering — Plant roots grow into rock fractures, exerting pressure as they expand, animals burrowing or human activities can also physically break rocks apart.

• e.g., tree roots breaking sidewalks or cracking bedrock.

• animals like earthworms loosening soil and breaking down small rocks.

Abrasion — Rocks and sediments grind against each other, wearing surfaces down over time.

• Often caused by wind, water, or ice movement.

• e.g., river rocks becoming smooth and rounded due to water flow; windblown sand carving grooves or shapes in exposed rocks, like those in deserts.

2. What are the different types of chemical weathering? Provide examples.

Chemical weathering — Involves the decomposition or alteration of minerals in rocks due to chemical reactions with water, air, or other chemicals.

• Unlike physical weathering, chemical weathering changes the mineral composition of the rock.

Hydrolysis — A chemical reaction between water and minerals, leading to the breakdown of silicate minerals and the formation of clay; water reacts with minerals like feldspar, replacing cations with hydrogen ions.

• e.g., common in humid environments, where water is abundant; feldspar in granite transforms into kaolinite clay.

Oxidation — Oxygen reacts with minerals, especially those containing iron, to form oxides. This reaction is similar to rusting and weakens the rock.

• e.g., iron-rich minerals like pyroxene and magnetite oxidize to form reddish-brown hematite or limonite; red, iron-stained rocks in deserts or mountainous regions.

Carbonation — Carbon dioxide from the atmosphere or soil dissolves in water to form carbonic acid, which reacts with carbonate minerals like calcite.

• Leads to the dissolution of the rock.

• e.g., the formation of stalactites and stalagmites in caves; limestone and marble dissolve in weakly acidic rainwater, creating caves and karst landscapes.

Dissolution (Acidification) — Water dissolves soluble minerals directly, often enhanced by acidic conditions.

• Common in minerals like halite (rock salt) or gypsum.

• e.g., halite dissolving in water, leading to the formation of salt flats; gypsum in dry climates dissolving to create sinkholes or subsidence.

Hydration — Minerals absorb water, causing their structure to expand and weaken.

• Involves physical addition of water molecules to the mineral structure.

• e.g., anhydrite transforms into gypsum when it absorbs water; clay minerals swell when they absorb water, leading to soil instability.

3. According to Bowen’s Reaction Series, which minerals are most stable during weathering?

According to Bowen’s Reaction Series, the stability of minerals during weathering is closely related to their crystallization temperatures.

• Minerals that crystallize at the highest temperatures are the least stable at the Earth's surface because they form under conditions far removed from surface environments.

• Conversely, minerals that crystallize at lower temperatures are more stable and resistant to weathering.

Relationship of Mineral Stability to Bowen’s Reaction Series:

1. Discontinuous Series: Olivine → Pyroxene → Amphibole → Biotite

   • Stability increases as you move down the series.

2. Continuous Series: Calcium-Rich Plagioclase → Sodium-Rich Plagioclase → Potassium Feldspar → Quartz

   • Stability increases as you move toward the silica-rich end.

Order of Stability (Most to Least Stable):

1. Quartz — Highly stable due to its low crystallization temperature, strong covalent Si-O bonds, and chemical inertness.

2. Muscovite Mica

3. Potassium Feldspar

4. Sodium-Rich Plagioclase

5. Biotite

6. Amphibole

7. Pyroxene

8. Calcium-Rich Plagioclase

9. Olivine — Least stable because its high crystallization temperature makes it poorly adapted to surface conditions like low temperatures and water-rich environments.

4. What conditions promote chemical weathering? Discuss factors such as climate and mineral composition.

Climate — The most important factor influencing chemical weathering, particularly temperature and precipitation.

• High Temperatures — Chemical reactions proceed faster at higher temperatures because reaction rates double with every 10°C increase.

  • Tropical regions with warm climates experience intense chemical weathering.

• Precipitation — Abundant rainfall provides water, the essential medium for chemical reactions like hydrolysis, dissolution, and carbonation; also promotes leaching, where water removes soluble materials from rocks and soils.

• Warm and humid climates (e.g., tropical rainforests) maximize chemical weathering due to the combination of heat and water.

Mineral Composition — The type of minerals present in a rock significantly affects its susceptibility to chemical weathering.

• High-Temperature Minerals — Minerals like olivine, pyroxene, and calcium-rich plagioclase feldspar, which crystallize at high temperatures, are less stable at Earth's surface conditions and weather quickly.

• Low-Temperature Minerals — Minerals like quartz and muscovite mica, which crystallize at lower temperatures, are more stable and weather slowly. Quartz is highly resistant due to its strong Si-O bonds and chemical inertness.

• Carbonate Minerals — Rocks like limestone and marble, composed of calcite, are highly susceptible to chemical weathering, especially carbonation and dissolution in acidic conditions.

Surface Area — Increased surface area (e.g., from physical weathering) promotes chemical weathering because more mineral surfaces are exposed to reactive agents like water and air.

• Fractured or porous rocks weather more rapidly.

Biological Activity:

• Plants and Microorganisms — Roots release organic acids that promote hydrolysis and carbonation; microbial activity can produce acidic compounds that enhance chemical weathering.

• Human Activities — Pollution increases the acidity of rainwater (acid rain), accelerating the dissolution of susceptible rocks like limestone.

Time — Longer exposure times allow chemical weathering processes to proceed more completely.

• Older rocks in stable landscapes often show advanced stages of chemical alteration.

Presence of Acids:

• Carbonic Acid (H₂CO₃) — Forms when CO₂ dissolves in water; drives carbonation.

• Organic Acids — Released by plants, accelerate the decomposition of minerals.

• Sulfuric Acid and Nitric Acid — From acid rain, intensify the chemical breakdown of rocks.

Mass Wasting (5)

1. What causes mass wasting? Discuss the key factors involved.

Mass wasting — Downslope movement of rock, soil, and debris under the influence of gravity.

• It is a natural geomorphic process that can be rapid or slow, depending on various factors.

Gravity — The fundamental cause of mass wasting, pulling materials downslope.

• The steeper the slope, the stronger the gravitational force acting on materials.

Slope Angle — Steeper slopes are more prone to mass wasting because the balance between gravitational force and resistance is easily disrupted.

• Oversteepening, such as from erosion or human excavation, can trigger slope failure.

Water — Alters the cohesion and weight of materials (e.g., adds weight, reduces friction, promotes lubrication, triggers liquefication).

• e.g., landslides after heavy rainfall or rapid snowmelt.

Rock & Soil Type:

• Weak Rocks and Soils — Loose, unconsolidated materials (e.g., sand, silt, or volcanic ash) are more prone to movement.

• Fractured or Weathered Rocks — Rocks with fractures, joints, or faults provide planes of weakness for sliding.

• Clay-Rich Soils — Clays swell when wet and shrink when dry, reducing slope stability.

Vegetation — Stabilizes slopes through root systems (binding soil particles and absorbing water).

Geological Structure:

• Bedding Planes and Faults — Rocks with bedding planes, faults, or foliation parallel to the slope are more prone to sliding.

• Dip Slope — When the rock layers dip in the same direction as the slope, they are more likely to slide.

Triggers — Events like earthquakes, volcanic activity, and heavy rainfall or snowmelt can initiate mass wasting.

Time:

• Long-Term Weathering — Gradual weakening of rocks and soils over time makes slopes more vulnerable to mass wasting.

• Cyclic Processes — Repeated freeze-thaw cycles, wetting and drying, or thermal expansion can cause gradual slope failure.

2. What are the different types of mass wasting and how do they vary in speed and movement style?

Slump — A rotational movement of a mass of rock or soil along a curved surface; movement occurs in discrete blocks rather than as a fluid mass.

• Speed: Moderate to slow (can take days to months).

• Commonly occurs in cohesive materials, such as clay-rich soils, on oversteepened slopes.

• Often triggered by water saturation or human activity.

• e.g., hillside slumps after heavy rainfall.

Rockslide — A sudden and rapid sliding of rock along a planar surface, such as a bedding plane or joint; the material moves largely as a unit or block.

• Speed: Fast (seconds to minutes)

• Common in steep, mountainous regions with fractured or tilted rock layers.

• Often triggered by earthquakes, rain, or freeze-thaw cycles.

• e.g., The Frank Slide in Canada (1903).

Debris Flow — A fast-moving, chaotic flow of a mixture of volcanic materials; highly fluid due to high water content.

• Speed: Fast (up to 50 km/h or more).

• Common in arid or semi-arid regions with little vegetation, where rainfall can quickly saturate the soil; often follows natural drainage channels.

• e.g., lahars (volcanic mudflows) on volcanic slopes like Mount Pinatubo.

Earthflow — A downslope flow of fine-grained material, such as clay or silt, that is less fluid than mudflows.

• Rapid

• Typically occur on hillsides in humid regions

• Water saturates the soil

• Liquefaction – a special type of earthflow sometimes associated with earthquakes.

Creep — The very slow, gradual downslope movement of soil or rock.

• Materials deform plastically under gravity, often caused by freeze-thaw cycles or wetting and drying.

• Speed: Extremely slow (millimeters to centimeters per year).

• Evidence includes bent tree trunks, tilted fences, and cracked foundations.

Solifluction — A type of creep specific to areas with permafrost or seasonally frozen ground.

• Occurs when the top layer of soil thaws and flows over the still-frozen layer below.

• e.g., arctic tundra slopes

3. How does water content (small vs. large amounts) impact soil cohesiveness?

Small Amounts of Water — Water molecules are able to bind to the soil particles through surface tension and adhesion, which increases the cohesion between particles.

• Increased cohesion and improved strength.

• e.g., dry clay soil

Large Amounts of Water — Water can reduce the friction between particles, weaken their cohesion, and even cause the soil to become mobile.

• Decreased cohesion, slippage and flow, soil liquefaction (slumping).

• e.g., after heavy rainfall, water-saturated clay or sandy soils can lose their strength and become prone to slippage or sliding down slopes.

  • Saturated soil on a steep slope is much more likely to experience a landslide or earthflow compared to dry soil.

4. Explain the concept of the angle of repose and its role in slope stability?

Angle of repose — The steepest angle at which a pile of loose material (such as sand, gravel, or soil) can remain stable without sliding or collapsing.

• Determined by the internal friction between the particles of the material, their shape, and the moisture content.

Factors Influencing Angle of Repose:

• Particle Size and Shape (Coarser, more angular materials = higher angle of repose).

• Moisture content (high moisture content = lower angle of repose).

• Material Type

Stable Slopes — If the slope angle is below the angle of repose, the slope will generally remain stable, as the forces holding the material in place (friction and cohesion) are greater than the force of gravity acting to move the material downslope.

Unstable Slopes — If the slope angle exceeds the angle of repose, the material is unstable and prone to mass wasting events, such as landslides, rockfalls, or debris flows.

• A steepened slope or over-steepened terrain, such as that caused by erosion or human activities like construction or excavation, can easily exceed the angle of repose, making the material on the slope more likely to fail.

Plate Tectonics (10)

1. How do ocean basins form? Compare the Pacific and Atlantic Oceans.

Ocean Basins — Deep underwater depressions formed primarily through the movement of tectonic plates.

Formation of Ocean Basins:

1. Divergent Boundaries — Ocean basins begin to form at divergent plate boundaries where tectonic plates move away from each other. As the plates pull apart, magma rises from the mantle to fill the gap, creating new oceanic crust. This process is known as seafloor spreading. Over time, the newly formed oceanic crust becomes part of the ocean basin floor, and the basin gradually expands.

   • The Mid-Atlantic Ridge is an example of such a divergent boundary, where the Atlantic Ocean is widening.

2. Subduction Zones and Ocean Basin Deepening — As oceanic plates continue to move, causing one tectonic plate dives beneath another, leading to deep ocean trenches (e.g., the Mariana Trench in the Pacific) and the deepening of ocean basins.

   • Volcanic activity from subduction zones can also contribute to the formation of island arcs and other underwater geological features.

3. Rifting and Continental Breakup — Occurs when a landmass begins to break apart due to tectonic forces, leading to the creation of an ocean basin (e.g., the Red Sea).

4. Sedimentation

Comparison of the Pacific and Atlantic Oceans:

2. What are the three types of plate boundaries, and how do they differ?

Divergent boundaries — Plates move apart, creating new crust (e.g., ocean ridges, rift valleys).

Convergent boundaries — Plates collide, leading to subduction, mountain building, or volcanic activity (e.g., mountain ranges, trenches).

Transform Boundaries — Plates slide past each other horizontally, causing earthquakes (e.g., fault lines).

3. What landforms result form plate boundary interactions? Discuss convergence of oceanic-continental. continental-continental and oceanic-oceanic plates. Why do these processes create specific landforms?

Oceanic-Continental Plate Convergence — The denser oceanic plate is subducted beneath the lighter continental plate.

• As the oceanic plate melts, magma rises to form volcanoes. The trench forms because the oceanic plate is pulled down into the mantle, creating a deep depression.

Landforms in Oceanic-Continental Plate Convergence:

• Ocean Trenches — The oceanic plate is forced into the mantle, creating deep ocean trenches at the subduction zone (e.g., Peru-Chile Trench).

• Volcanic Arcs — Chain of volcanoes on the continental plate due to oceanic plate subduction (e.g., Andes Mountains and Cascade Range).

Continental-Continental Plate Convergence — Neither plate is subducted due to their similar densities. Instead, they crumple and fold, forming large mountain ranges and other features.

Landforms in Continental-Continental Plate Convergence:

• Mountain Ranges (e.g., Himalayas and the Alps)

• Plateaus (e.g., Tibetan Plateau).

Oceanic-Oceanic Plate Convergence — One of the plates is subducted beneath the other, forming a deep ocean trench. The subducted oceanic plate melts, and magma rises to form a chain of volcanic islands.

• As the subducted plate melts, volcanic activity forms an island arc on the overriding plate.

Landforms in Oceanic-Oceanic Plate Convergence:

• Ocean Trenches (e.g., Mariana Trench)

• Volcanic Island Arcs (e.g., Aleutian Islands)

4. Where are earthquakes commonly found along these plate boundaries, and why?

Divergent Boundaries to Earthquakes — As plates separate, tension builds up, especially along fault lines where the plates move. The resulting stress can cause the crust to crack or fracture, leading to earthquakes.

• In rift zones, as the crust stretches and weakens, it can produce seismic activity.

• These earthquakes are generally shallow, occurring near the surface.

• e.g., mid-ocean ridges such as the mid-Atlantic ridge and continental rifts like the east African rift.

Convergent Boundaries to Earthquakes — In subduction zones, the collision and subduction of one plate beneath another create immense pressure, causing the plates to get "stuck." When this pressure is released, it results in an earthquake. These earthquakes can be shallow or deep depending on the depth of the subducting plate. In continental collision zones, the plates press against each other and deform, often forming large mountain ranges (e.g., the Himalayas). The stress and strain from the collision can cause intense seismic activity.

• Earthquakes at these boundaries can range from shallow to deep depending on the nature of the collision.

• e.g., subduction zones: Where an oceanic plate is subducting beneath a continental plate (e.g., Peru-Chile Trench), or where one oceanic plate subducts beneath another (e.g., the Mariana Trench).

• e.g., continental collision zones such as the Himalayas.

Transform Boundaries to Earthquakes — As the plates move laterally past each other, the friction along the fault line causes stress to accumulate. When the stress exceeds the strength of the rocks, it is released in the form of an earthquake.

• These earthquakes are usually shallow.

• e.g., fault lines, such as the San Andreas Fault in California and the Alpine Fault in New Zealand.

5. Explain the Continental Drift Theory. What are its key ideas, and what are its limitations?

Continental Drift Theory (Alfred Wegener, 1912) — Earth's continents were once part of a supercontinent called Pangaea, which began to break apart and drift to their current positions over millions of years.

Pangaea — The supercontinent, composed of all of Earth’s continents, around 300 million years ago.

• Eventually began to break apart during the Mesozoic Era, about 200 million years ago, leading to the formation of the continents we know today.

Evidence for Continental Drift:

• Fossil Evidence (similar fossils in different continents)

• Geological Evidence (geologically similar mountains in diff. continents)

• Climatic Evidence (glacial deposits and other climatic evidences)

• Fit of the Continents

Limitations of the Continental Drift Theory:

1. Lack of Mechanism

2. Insufficient Evidence (seafloor spreading and ocean ridges have not yet been discovered).

3. Opposition from Geophysicists (lack of credentials).

• While Wegener's Continental Drift Theory faced criticism, it laid the groundwork for the development of the more comprehensive Plate Tectonics Theory in the 1960s. New evidence from the study of the ocean floor, such as magnetic striping on the ocean floor and the discovery of mid-ocean ridges, provided crucial evidence that supported the idea of seafloor spreading. This, along with the development of a mechanism for plate movement (convection currents in the mantle), explained how continents could drift over time.

Volcanoes (5)

1. What is a volcano, and what causes its formation?

Volcano — Opening or a rupture in the Earth's surface through which molten rock (magma), gases, and ash are ejected from below the Earth's crust.

• Occurs when magma from the mantle rises through the crust and emerges on the surface, creating a volcanic eruption.

• Typically associated with mountain-like landforms that gradually grow over time due to successive eruptions.

Causes of Volcano Formation:

• Subduction Zones (Convergent Boundaries) — One plate is forced beneath another, causing magma to rise and form volcanoes.

• Rift Zones (Divergent Boundaries) — Plates pull apart, creating space for magma to rise and form volcanoes.

• Hotspots — Stationary magma plumes in the mantle create volcanoes as plates move over them.

• Continental Collisions — Intense pressure and heat from colliding continental plates can also cause volcanic activity.

2. Differentiate between magma and lava.

Magma — Molten rock found beneath the Earth's surface, in the mantle or in the crust. It consists of a mixture of molten rock, gas, and crystals.

• Located underground, within the Earth's mantle or crust.

• Composed of molten rock (silicates, oxygen, and various minerals), dissolved gases (such as water vapor, carbon dioxide, and sulfur dioxide), and crystals of minerals.

• Forms due to intense heat and pressure in the Earth's interior, which causes solid rock to melt.

Characteristics of Magma:

• It is viscous and often thick.

• Magma is typically stored in magma chambers beneath the Earth's surface.

• It is hotter and more pressurized than lava.

Lava — Magma that has reached the Earth's surface during a volcanic eruption. Once it erupts from the volcano, it is called lava.

• Located above ground after an eruption, on the surface of the Earth.

• Composed the same as magma, though it may lose some of its dissolved gases as it erupts and comes into contact with the atmosphere.

Characteristics of Lava:

• Lava is generally less viscous than magma because it has lost much of its dissolved gases.

• Lava flows across the ground and cools to form volcanic rock (e.g., basalt or pumice).

• It is slightly cooler than magma and has a lower pressure when it reaches the surface.

3. Describe the three main types of volcanoes, including their structural and process-related characteristics.

Shield Volcanoes — Broad, gently sloping sides that resemble a warrior's shield (e.g., Hawaii’s Mauna Loa and Kīlauea)

• They are typically wide with a low, convex profile and are built up over time by non-explosive eruptions of low-viscosity basaltic lava that flows easily and spreads out.

Eruption Style of Shield Volcanoes:

• Erupt with gentle lava flows that travel over long distances.

• The lava produced is typically basaltic, which is low in silica and high in iron and magnesium, making it less viscous and allowing it to flow easily.

• These volcanoes rarely have explosive eruptions due to the fluid nature of their lava, which allows gases to escape easily.

Stratovolcanoes (Composite Volcanoes) — Have steep, conical slopes and are often symmetrical in appearance, formed by alternating layers of solidified lava flows and pyroclastic materials (such as ash, tephra, and volcanic rocks) (e.g., Mount Fuji).

• These volcanoes are typically larger than shield volcanoes and have a more complex structure, often with a central crater or caldera.

Eruption Style of Composite Volcanoes:

• Tend to have explosive eruptions that can be highly destructive. This is due to the high-viscosity and gas-rich nature of their lava, which prevents gas from escaping easily.

• The lava produced is usually andesitic or rhyolitic, which is more silica-rich and more viscous than the basaltic lava of shield volcanoes.

• The eruptions often produce pyroclastic flows, ash clouds, and lava domes, and can result in significant hazards like lahars (mudflows).

Cinder Cone Volcanoes — Smallest of the three types and are characterized by steep slopes. They are conical in shape and often have a small crater at the summit (e.g., Sunset Crater in Arizona).

• These volcanoes are formed by the accumulation of pyroclastic material, such as ash, cinders, and volcanic debris, which is ejected during explosive eruptions and falls back around the vent to create a cone-shaped mound.

Eruption Style of Cinder Cone Volcanoes:

• Cinder cone eruptions are typically short-lived but violent. They produce moderate explosions that eject gas-charged lava fragments, which cool and solidify in the air, falling as pyroclasts (e.g., ash, cinders).

• The lava that erupts is generally high in viscosity, often andesitic or basaltic, leading to more explosive eruptions compared to the gentle flows of shield volcanoes.

• Cinder cones often form rapidly but are relatively small and not as widespread as other types of volcanoes.

4. What are some examples of volcanic hazards? Define pyrolastic flow and their impacts.

Pyroclastic Flow — Fast-moving hot gas, ash, and rock that can destroy everything in its path.

Lava Flows — Molten rock that destroys structures and alters landscapes.

Ash Fall — Falling volcanic ash that can cause health issues, disrupt air travel, and damage agriculture.

Lahars — Mudflows composed of volcanic debris and water, causing destruction and flooding.

Volcanic Gases — Toxic gases that can impact air quality and lead to suffocation or climate changes.

Volcanic Earthquakes — Seismic activity that can damage infrastructure and trigger other hazards.

Earthquakes (5)

1. What are seismic waves? How do P-waves, S-waves, and surface waves differ?

Seismic waves — Vibrations that travel through the Earth, generated by events like earthquakes or volcanic activity.

• Move through the Earth’s interior and along its surface, transmitting energy from the source to distant locations.

Primary Waves (P-Waves) — Compressional waves, meaning they move by alternately compressing and expanding the material they travel through.

• These waves move in the same direction as the wave itself (longitudinal motion).

• P-waves are the fastest seismic waves, so they are the first to be detected by seismographs.

• They can travel through both solids and liquids (such as the Earth’s liquid outer core).

Secondary Waves (S-Waves) — Shear waves, meaning they cause the material to move perpendicular to the direction of wave propagation.

• These waves move in an up-and-down or side-to-side motion (transverse motion).

• S-waves are slower than P-waves and are typically detected after P-waves.

• S-waves can only travel through solids, which is why they do not pass through the Earth’s liquid outer core.

Surface Waves — Travel along the Earth's surface, causing the most ground movement and damage during an earthquake.

• There are two main types of surface waves—Love waves and Rayleigh waves.

• Slower than both P-waves and S-waves but are usually the most destructive because they involve larger ground displacements.

Love Waves — Cause horizontal shearing, similar to S-waves but confined to the surface.

Rayleigh Waves — Move in an elliptical motion, both up-and-down and side-to-side, like ripples on water.

2. What are the main parts of an earthquake? (focus, epicenter, fault)

Focus — Exact point inside the Earth where the earthquake originates. This is where stress built up along a fault is suddenly released, causing seismic waves to radiate outward.

• It is located beneath the Earth’s surface, at varying depths depending on the earthquake.

• The depth of the focus influences the intensity and reach of the earthquake. Shallow-focus earthquakes (less than 70 km deep) tend to cause more damage than deeper ones.

Epicenter — The point on the Earth’s surface directly above the focus, it is a surface-level projection of the focus.

• This is typically the location where the earthquake’s effects, like shaking, are strongest because it is closest to the energy release.

Fault — A fracture or zone of fractures in the Earth’s crust where two blocks of rock move past each other.

• Planes along which the Earth’s crust slips during an earthquake.

• Faults are critical to understanding earthquake mechanics, as the type and movement along a fault dictate the nature of the earthquake.

Movement Types of Faults:

• Normal faults: Caused by extensional forces, where one block moves down relative to the other.

• Reverse (or thrust) faults: Caused by compressional forces, where one block moves up over the other.

• Strike-slip faults: Caused by horizontal shearing forces, where the blocks slide past each other laterally (e.g., the San Andreas Fault).

3. Explain the difference between intensity and magnitude. How are they measured?

Intensity — Perceived strength or effect of an event at a specific location.

• Subjective measure based on human observations and the damage or impact of the event.

Measurement of Intensity:

• Modified Mercalli Intensity (MMI) scale for earthquakes, which rates the intensity from I (not felt) to XII (total destruction). For light, intensity can be measured in terms of lux (the amount of light reaching a surface) or luminous intensity (measured in candelas).

Magnitude — Measures the overall size or energy released by an event.

• An objective measure that does not depend on location or human perception.

Measurement for Magnitude:

• Richter scale for earthquakes, which assigns a number (e.g., 5.0, 7.0) based on the amplitude of seismic waves recorded by seismographs.