Test 2

SAND                  SILT                       MUD

High energy ------------------> Low energy

river-dominated deltas are branch shaped (birdsfoot?) eg. Mississippi

wave-dominated deltas are more fan-shaped eg. Nile

tide-dominated deltas have bays of sediment eg Ganges or Maracaibo 

Processes remain the same

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'PROGRADATION' is the movement of sediment into the delta

the energy levels are higher at the beginning of the delta (the delta plain), and lower nearer the sea (the prodelta).

Limestone Case Study-Reefs

Modern reefs are mainly equatorial

Formation:

1. A volcano rises from the ocean floor

2. The volcano eventually becomes extinct and begins to erode. A fringing reef forms at the base of the volcano

3. The volcanic island subsides as the reef builds up, forming a lagoon in the middle of the reef. There may still be a remnant of the island above sea level.

4. With continued subsidence, the reef completely covers the buried island.

Why do they occur?

-Movement at plate boundaries and plate margins

What happens?

-Quakes: rock builds pressure, becomes elastic, breaks and releases energy

-Volcanoes: hot magma rises in the rocks and makes its way to the surface where it erupts or oozes out

How do we predict?

-History: has it happened before?

-Strange topography: is there landscape evidence (offset rivers, ridges, tilted trees, etc)?

-Seismometers, global positioning systems

-Animal behaviour

How do we cope?

-Building standards and regulations, not developing in high-risk areas, etc. 

-Earthquake safety programs and education.

What are the benefits?

-Volcanoes: fertile ground, microclimate, associated tourism (eg, Hawaii), geothermal energy

-Quakes: seismic networks are useful for managing quakes, landslides and explosions.

4.6 billion years ago the Sun's output was only 70% of the present.

With today's atmosphere, this would mean that the earth would've been around -25oC.

Yet there is proof that there was liquid water on earth.

How could this be? There must have been a lot of greenhouse gases in the atmosphere keeping the earth warm.