Oceans The Basics Overview of Oceans Covers 23

Oceans The Basics

Overview of Oceans • Covers 2/3 rds of Earth’s surface • Average depth 3800 m (2. 4 miles) • Deepest spot 11022 m (6. 8 miles) • 97% of Earth’s water in ocean • More water trapped in Earth’s interior than in oceans

Origin of Oceans • Earth 4. 6 billion yrs old • Density stratification – Heavy elements/minerals [Fe] fall to bottom – Lighter ones float to top (and vapors) • Outgasing – Vapors condense into clouds RAIN – 10 million yrs of rain weathered & dissolved rock, created salty oceans

5 Major Oceans • Pacific • Atlantic • Indian • Southern • Arctic

Seawater • Salinity – amount of salt in water – Average 3. 5% total (Na. Cl, K, Mg, Ca) – Some places are saltier than others. • Salt comes from weathering & erosion of rocks on land (chemical weathering) • Estuaries – large river flows into ocean and makes water less salty. – EXAMPLES: Amazon River, Mississippi R. • Glaciers melting provides fresh water too.

Ocean Layers • Surface/mixed layer [0 -250 m] – temp & salinity relatively constant – [2% of ocean] • Thermocline/Pycnocline/Halocline [250– 1000 m] – Rapid change in temperature, density, & salinity with depth [18% of ocean] • Deep layer [under 1000 m] – Relatively constant density, cold temps – [80% of ocean]

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