1. Oceans Lesson 1: Composition and Structure
Objective: What are Oceans and why are they so important?

2. Earth: “Water Planet or Blue Planet”
REVIEW!!!
Water covers 70% of Earth’s surface
97% salt water, 3% Freshwater
5 OCEANS: All interconnected
Pacific- largest/deepest
Atlantic – ½ size of Pacific, 20% of Earth’s surface
Indian – 3rd largest
Southern – surrounds Antarctica – Ice covers some surface all year
Arctic – near North Pole. Some surface is ice covered all year
Average depth of ocean : 4,000 m.

3. Formation of the Oceans
Evidence that oceans formed 4.2 billion years ago
Many volcanoes covered Earth making it very hot
Erupted huge amounts of gas (including water vapor, CO2, etc..)
Forming atmosphere
As Earth cooled – condensation and precipitation over thousands of years
Eventually forms Earth’s oceans.
Additional Source: Asteroids and Comets

4. Seawater Formation & Composition
Precipitation over rocks and minerals – rivers flow into ocean.
Gases from ancient volcanic eruptions
Salinity: Measured in parts per thousand (ppt)
Brackish water – fresh mixed with seawater – where river enters ocean.

5. Seafloor Continental Margins: Part of ocean basin next to continent
From shoreline to deep ocean
3 Regions:
Abyssal Plains: Covered by thick layers of sediment
Mid-Ocean: Where tectonic plates pull apart. Continuous mountain range extends through all of Earth’s ocean basins
Ocean Trenches: Deepest part of the ocean. Forms when plates collide
Resources from Seafloor:
Energy: oil, natural gas, methane hydrates
Minerals: most in abyssal plains

6. Zones in Ocean Ocean is divided by physical characteristics
Sunlight, temperature, salinity, density
Surface: Shallow, most sunlight of all zones. Most organisms that perform photosynthesis live here
Middle: Only receives blue/green light
Deep: Plants don’t grow here – no light. “Midnight Zone”

7. Wavelengths of Light Order absorbed by the ocean water:
First: red and violet
Last: green and blue