3.4: The Earth’s Water (Oceanography)

River

A large stream of freshwater that flows downhill in a channel.

Parts of a stream

Source (high mountains/spring)

Confluence - where 2 streams meet (+Tributary: smaller of 2 streams)

Mouth - where stream enters larger body of water (lake/ocean)

Estuary - where stream meets ocean/lake

Stages of a stream

Headwaters - where stream forms

Meander - bend/curve in a stream channel; develops when a stream

• Moves into lower area, gradient not as steep

• Does more work eroding the edges of its banks

Floodplain - where water from stream OVERFLOWS during floods

Base level - where stream meets large body of standing water

Estuary

Semi-enclosed coastal body of water with 1+ rivers or streams flowing into it, and with a free connection to the open sea

Often associated with high levels of biological diversity

Characteristics of estuary

Typically the tidal mouths of rivers

Characterized by sedimentation or silt carried in from terrestrial runoff, freq from offshore

Made up of brackish water

Often given names like bay, sound, fjor

Global ocean

The idea that oceanic water mass comprises of one global, interconnected body of salt water, known as world ocean or global ocean

Major oceanic divisions (in descending order of size)

Pacific Ocean

Atlantic Ocean

Indian Ocean

Southern Ocean

Arctic Ocean (sometimes considered a sea of the Atlantic)

The ocean covers _ of the earth’s surface.

3/4

Tides

The rising of the earth’s ocean surface caused by the tidal forces of the moon and the sun acting on the oceans

What is the main cause of tides on Earth?

The gravitational attraction of the moon is the main cause of tides.

How does the sun affect tides?

The sun’s gravity also pulls on Earth’s oceans, making tides higher or lower depending on the positions of the sun and moon.

Tidal streams

Changes in the depth of the marine and estuarine water bodies caused by tides, resulting in oscillating currents

Semidiurnal tides

2 high waters, 2 low waters / day

Diurnal tides

1 tidal cycle / day

Spring tides

Happens around a new/full moon

When the sun, moon, and earth forms a straight line → tidal forces from the sun reinforce those of the moon

When the tide’s range is at a maximum

Neap tides (neaps)

When the moon is at 1st quarter or 3rd quarter

The sun and moon are separated by 90° when viewed from the earth.

Forces induced by the sun partially cancel those of the moon

When the tide’s range is at a minimum

How does coastal topography affect tides?

The shape of the coastline and ocean floor can change how high or low tides are in a specific area.

Why do some places have bigger tides than others?

Local features like bays, inlets, and the slope of the sea floor can amplify or reduce the size of tides.

Tidal force produced by the sun is % as _ as that produced by the moon

46% as large as that produced by the moon.

Causes of tides

Gravitational attraction between the moon and the earth

🌜 Gravitational attraction of the moon causes the oceans to bulge out on the side of the earth facing the moon. 

Another bulge also occurs on the opposite side of the earth as the earth is being pulled toward the moon. 

Due to the rotation of the earth, two tides occur each day