 Your Objectives:  Use the density formula to correctly figure the density of granite (continents) and basalt (ocean).  We will discuss why the ocean floor (basalt) is lower than the continents (granite).  Correctly differentiate between very salty water (most dense) and less salty water.

What letter corresponds to each number? 1) ____ High Tide 2) ____ Neap Tide 3) ____ Low Tide 4) ____ Spring Tide a) Higher high tide and lower low tide cause by alignment of sun, earth and moon (during full and new moons) b) Lower high tide and higher low tide caused by 90 degree alignment of sun, earth, and moon (during first and third quarter moons) c) Bulge in the ocean on the side facing the moon and on the opposite side. d) Lowest level of the ocean that occurs between the two high tides. Answers 1)C 2)B 3)D 4)A

 The continents are formed mainly out of granite rocks.  The ocean floor consists of rocks called basalt.  Why does the ocean floor sink lower into the mantle than the continents?  Density Demo

 Granite is igneous rock that is formed when magma solidifies within the crust or mantle.  Granite is about 3.8 billion years old.  Basalt hardly ever exceeds.1 billion years old. Why? This is because the oceanic crust is constantly being replaced with molten material that climbs upward from the mantle.

 The reason that the continents stand higher than the ocean basins is that the oceanic crust is more dense (3.2 g/cm³) than the continental crust (2.7 g/cm³).  The oceans take up 3/4 (.71%) of the earth's surface.  What is in the ocean? Salty water, diverse life forms, dissolved gases, minerals, and nutrients.

 Demo  Why did the egg sink to the bottom in the first container?  Why did the egg float in the second container?

 Salinity: The amount of dissolved salts in the water  Temperature and Salinity affect the density of water.  Very salty waters are more dense and will sink lower in the ocean.  Less salty water is less dense and will float on top of more dense salty water.

 We used the density formula to figure out the continents density and oceans density.  What is the formula?  Which is more dense?  We learned how the oceans salinity affects the density of water.  This information will be useful for studying for the test tomorrow.  Any questions?  Starting Tuesday, we begin Physics!