Marine Geology and Earth Structure Quiz

Marine Geology, Chemistry, Physics

• Oceans cover approximately 71% of Earth's surface.
• The Northern Hemisphere is 61% ocean, while the Southern Hemisphere is 80% ocean.
• Ocean basins are categorized as Pacific (largest and deepest), Atlantic (roughly equal), Indian (roughly equal), and Arctic (smallest and shallowest).

Structure of the Earth

• Density decreases from the center outward.
• The crust (both oceanic and continental) is akin to ice chunks floating on water (mantle).
• All life on Earth is influenced by the mantle's movement.

Oceanic and Continental Crust

• Oceanic crust has a density of 3.0 g/cm³.
• Oceanic crust is young and dark, primarily composed of basalt rich in iron and magnesium.
• Continental crust has a density of 2.7 g/cm³.
• Continental crust is old and light, mainly composed of granite with sodium, potassium, and quartz.

Plate Tectonics

• Sir Francis Bacon suggested that continents were once one large supercontinent.
• Alfred Wegener proposed continental drift in 1912.
• Pangea was a single supercontinent that existed 180 million years ago.
• Wegener questioned continental connections and the forces causing separation.
• Evidence for continental drift includes continental margin configuration matching (75%), matching rocks and fossils across the Atlantic, rock magnetism, and ocean bedrock age (nothing older than 175 million years; oldest land rocks 3.9 billion years).

Plate Boundaries

• Divergent: Plates move apart, creating new oceanic crust (Mid-Atlantic Ridge).
• Convergent: Plates collide, resulting in trenches and potentially volcanic arcs (Mariana Trench, Japan, Andes).
• Compression: Continental plates collide creating mountain ranges (Himalayas).
• Lateral (Transform): Plates slide past each other (San Andreas Fault).

Marine Sediments

• Particle size indicates origin and transport method.
• Shape reflects different transport distances.
• Color reflects composition (white - calcium carbonate, black - high organic matter, red - iron oxide, gray - high silica).
• Pelagic sediments come from processes within the ocean.
• Biogenous sediments are composed of microscopic organisms' skeletons/shells.
• Inorganic sediments are primarily clay (70%), often carried from land by currents.
• Volcanic sediments are from volcanic activity.
• Lithogenous sediments are derived from land rock breakdown.

Properties of Water

• Water exists in three states (liquid, gas, solid).
• Water has a high boiling point (100°C).
• Viscosity of water increases as temperature decreases.
• Ice is less dense than water (allows it to float).
• Water has a high heat capacity which moderates temperature changes in coastal areas.
• Surface tension allows some organisms to "walk" on water.
• Water is a solvent, dissolving more substances than any other liquid.

Seawater Composition

• Salinity measures dissolved salts in seawater.
• Common salts include chloride, sodium, magnesium, calcium, and potassium.
• The overall salinity percentage remains relatively constant (3.5% or 35 ppt).
• Salinity ratios remain consistent, even though precipitation and evaporation can cause local variations.
• Factors affecting salinity include evaporation, rainfall, and river runoff.

Ocean Depth Profiles

• Salinity, temperature, and density change with depth.
• The halocline is the zone of rapid salinity change below the surface, stabilizing at a consistent level.
• The thermocline is the layer of rapid temperature change beneath the surface layer.
• The pycnocline is the layer where density changes rapidly below the thermocline.

Dissolved Gases

• Seawater contains oxygen (0-9%) used by organisms. Oxygen levels decrease with depth and are highly affected by wind-driven motion and turbulence.
• Carbon dioxide is essential for photosynthesis.
• Nitrogen is necessary for building amino acids and proteins; it must be converted into other usable forms for organisms.

Transparency

• Seawater is relatively transparent, depending on suspended particles.
• Turbidity measures cloudiness.
• Light penetrates to different depths, affecting light-dependent processes like photosynthesis.
• Different colors of light penetrate to varying depths (red -> blue).

Water Movement

• Waves are initiated by wind, affected by wind speed, fetch (contact area), and topography. Water molecules move, but do not travel with the wave.
• Plunging waves occur on steep slopes.
• Spilling waves occur on gently sloping beaches.
• Surging waves occur on vertical cliffs.
• Currents are large-scale water movements caused by wind, density, Earth's rotation, and tides.

Tides

• Tides are caused by the gravitational pull of the sun and the moon, and the Earth's rotation.
• Diurnal tides have one high and one low tide per day.
• Semi-diurnal tides have two high and two low tides per day.
• Mixed semi-diurnal tides have two high and two low tides of unequal heights per day.

Monthly Tidal Cycle

• Spring tides occur when the sun, moon, and Earth are aligned (full and new moon).
• Neap tides occur when the sun, moon, and Earth are at right angles (first and third quarter moon).
• The cycle repeats every 28 days.

Vertical Water Movements

• Sinking cold water (overturn).
• Upwelling brings nutrient-rich water to the surface.
• Downwelling moves heat and oxygen to the deep ocean.
• Coriolis Effect causes deflection of water.
• Ekman transport causes spiraling of water due to wind.
• Various surface currents exist based on wind systems, density differentials and position relative to continents. and other topographical features.