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

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.

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

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.

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

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”

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