AICE Marine Objective Notes

75% of Earth’s surface covered with water
71% of Earth's surface is seawater
97% of surface water is in oceans; less than 3% in freshwater sources (lakes, rivers, etc.)

Earth is density stratified; deeper layers are denser.
Density: Relationship of mass to volume, calculated as
$\text{Density} = \frac{\text{mass}}{\text{volume}}$
Deepest hole dug: 12,063 m (7.5 miles), impacted by temperature and pressure.
Layers differentiated by composition and physical properties:
- Crust: 0.4% of Earth's mass, thin outermost layer. Oceanic crust (basalt) denser than continental crust (granite).
- Mantle: 68% of mass, made of silicon, oxygen, iron, and magnesium, 1,800 miles thick.
- Core: Innermost layer, predominantly iron and nickel, extremely dense and solid due to pressure.

Frances Bacon (1620): Noticed jigsaw fit of continental shorelines.
Edward Suess (1885): Identified similar fossils across coasts, unable to explain why.
Alfred Wegener (1912): Proposed Continental Drift hypothesis, supported by:
- Similar shorelines and fossils.
- Glacial erosion patterns across continents.
- Discovery of coal in Antarctica, indicating warmer climates.

Deep earthquakes align with mid-ocean ridges.
Older ocean floor is thicker, while newer floor is found near spreading centers.
Max age of ocean floor: 200 million years, contrasting with Earth's age of 4.5 billion years.
New oceanic crust forms at spreading centers; cools and densifies moving away.
Plate Tectonics Theory (1965, John Tuzo Wilson): Earth’s outer shell consists of about a dozen tectonic plates floating on the mantle.

Divergent Boundaries: Plates moving apart (e.g., oceanic crust formation).
Convergent Boundaries: Plates moving toward each other (subduction of oceanic beneath continental, forming volcanic arcs).
- Oceanic-Continental: Oceanic subducted, causing volcanic activity.
- Continental-Continental: Formation of mountain ranges (e.g., Himalayas).
- Oceanic-Oceanic: Older, denser plate subducted, resulting in volcanic islands (e.g., Japan).
Transform Boundaries: Plates slide past each other, creating earthquakes without new crust formation.

Reveals Earth's magnetic field history through magnetite alignment in cooling magma.
Symmetrical magnetic strips indicate seafloor age and movement.

Mid-Ocean Ridges: Largest geological features, formed by upwelling magma.
Hydrothermal Vents: Form when seawater interacts with magma, creating mineral-rich outflows.
Abyssal Plains: Flat ocean floor covered with sediment, typically found between ocean ridges.
Trenches: Formed at convergent boundaries, some of Earth’s deepest features (e.g., Mariana Trench at 11,022 m).
Volcanoes: Form through subduction (convergent) or mantle plumes (hotspots).

Earthquakes: Result from built-up pressure along fault lines released suddenly.
Tsunamis: Large sea waves caused by underwater earthquakes; destructive in shallow coastal areas.

Weathering: Breakdown of rocks into smaller pieces via various natural processes:
- Chemical Weathering: Alteration of rock composition through exposure to elements (e.g., rainfall).
- Physical Weathering: Mechanical breakdown without chemical change (freeze-thaw cycles).
Erosion: Movement of materials by agents like water, wind, and ice.
Sedimentation: Accumulation of particles at new locations, influenced by water speed and particle size.

Littoral Zone: Area between high and low tide, influenced by substrate and wave action.
- Substrate types: rocky, sandy, muddy, estuaries, deltas (each affecting coastal stability).
Ocean Currents: Driven by wind, temperature, and salinity variations, includes surface and deep currents.
Coriolis Effect: Deflection of currents due to Earth’s rotation.

Upwelling: Cold, nutrient-rich water rising to the surface, crucial for marine productivity.
Downwelling: Movement of surface water downward, influenced by wind.
Thermohaline Circulation: Global movement of ocean waters due to temperature and salinity differences.

El Niño: Period of warmer sea surface temperatures in the Pacific, affecting global weather patterns.
Tides: Regular changes in ocean levels influenced primarily by gravitational forces from the moon and sun.
- Spring Tides: Maximum tidal ranges during full and new moons.
- Neap Tides: Minimum tidal ranges during first and third quarter moons.

Hydrothermal vents form in extreme environments affecting local ecosystems, such as Tevnia tube worms:
- Symbiotic relationships with chemosynthetic bacteria.
Experiments may investigate environmental pressures on larval attachment and effects of pH on habitat suitability.