oceanography

What is the Wentworth Scale used for?

Classifying sediment based on grain size.

What are diatoms made of?

Silica (SiO₂); they are photosynthetic and contribute to fossil fuel formation.

What is phosphatic ooze?

Ocean sediment rich in phosphate from decayed organic matter.

What are test shells in micro-organisms?

Hard coverings made of silica or calcium carbonate, found in plankton like foraminifera.

What do coccolithophores secrete?

Calcareous (calcium carbonate) plates.

What are the White Cliffs of Dover made of?

Chalk, a form of limestone from coccolithophores' shells (carbonate deposits).

What happens at the lysocline?

Rapid dissolution of calcium carbonate (calcite).

What causes spring tides?

Alignment of sun and moon during new or full moon—greatest tidal range.

What causes neap tides?

Sun and moon at right angles during quarter moons—smallest tidal range.

What is declination?

Angular distance of the sun or moon above or below Earth’s equator.

What is aphelion?

Point when Earth is farthest from the sun (in July).

What is perihelion?

Point when Earth is closest to the sun (in January).

What is perigee?

Moon’s closest point to Earth—causes the greatest tidal effects.

What is apogee?

Moon’s farthest point from Earth—causes weaker, smaller tides.

What is a diurnal tide?

One high tide and one low tide per day.

What is a semidiurnal tide?

Two high tides and two low tides per day, roughly equal in height.

What is a mixed tide?

Two high tides and two low tides per day, with unequal heights.

What is tidal range?

The vertical difference between high tide and low tide.