Earth Science: Oceanography

Which ocean layer, extending from the surface to approximately 200 meters, is the only zone where enough sunlight penetrates for photosynthesis?

The epipelagic zone (or photic zone) is the uppermost layer of the ocean where light levels are sufficient for primary production by phytoplankton.

What geological feature is formed at divergent plate boundaries where new oceanic crust is created through volcanic activity?

Mid-ocean ridges are continuous underwater mountain ranges formed by seafloor spreading and the upwelling of magma.

What is the term for the total mass of dissolved inorganic solids in a kilogram of seawater, typically expressed in parts per thousand (ppt)?

Salinity is the measure of dissolved salts in water, with an average ocean value of approximately 35 g/kg or 35 ppt.

During which moon phases do spring tides occur, resulting in the highest high tides and lowest low tides?

Spring tides occur during the New Moon and Full Moon phases when the Earth, Moon, and Sun are aligned in syzygy.

What type of coastal ecosystem is characterized by a semi-enclosed body of water where freshwater from rivers mixes with salty ocean water?

An estuary is a highly productive transition zone between river and ocean environments containing brackish water.

Which part of the continental margin is the gently sloping, submerged surface extending from the shoreline toward the deep-ocean basin?

The continental shelf is the shallowest part of the continental margin, typically extending to a depth of about 200 meters.

What drives the 'Great Ocean Conveyor Belt,' and what are the two primary variables that determine the density of the water involved?

Thermohaline circulation is driven by density gradients created by variations in temperature (thermo) and salinity (haline).

In the mesopelagic zone, what is the name of the layer where water temperature drops rapidly with increasing depth?

The thermocline is the transition layer between warmer mixed surface water and the cold deep water where temperature decreases significantly.

Explain the process of coastal upwelling in the Northern Hemisphere when winds blow from the North along a West coast.

Coastal upwelling occurs when winds move surface water offshore due to Ekman transport (90 degrees to the right of wind), pulling cold, nutrient-rich water from depth to the surface.

Describe the chemical reaction that occurs when CO2 is absorbed by seawater, leading to ocean acidification.

CO2 reacts with water to form carbonic acid (CO2 + H2O ⇌ H2CO3), which dissociates into hydrogen ions (H+) and bicarbonate (HCO3-), thereby lowering the pH.