The Earth has two different types of crust: Continental crust and Oceanic crust. Each has different properties and therefore behaves in different ways. Continental crust: Continental crust forms the land (the continents, as the name suggests) that we see today. Continental crust averages about 35 km thick. Under some mountain chains, crustal thickness is approximately twice that thickness (about 70 km thick). - The mountains we see on earth have deep roots in the crust that we can’t see. The crust “floats” on the more dense mantle and, like how only the tip of an iceberg sticks up out of the water, we see only the tip of the continental crust - the mountain ranges. Continental crust is less dense and therefore more buoyant than oceanic crust Continental crust contains some of the oldest rocks on Earth. - Ancient rocks exceeding 3.5 billion years in age are found on all of Earth's continents. The oldest rocks on Earth found so far are the Acasta Gneisses in northwestern Canada near Great Slave Lake (4.03 Ga) [Ga = billion years ago] and the Isua Supracrustal rocks in West Greenland (3.7 to 3.8 Ga), but well-studied rocks nearly as old are also found in the Minnesota River Valley in the USA (3.5-3.7 billion years), in Swaziland (3.4-3.5 billion years), and in Western Australia (3.4-3.6 billion years). Oceanic crust: As the name already suggests, this crust is below the oceans. Compared to continental crust, Oceanic crust is thin (6-11 km). It is more dense than continental crust and therefore when the two types of crust meet, oceanic crust will sink underneath continental crust. The rocks of the oceanic crust are very young compared with most of the rocks of the continental crust. They are not older than 200 million years.
Atmosphere, hydrosphere, and lithosphere (1)
Hydrosphere and Lithosphere
Earth System (4 physical systems)• Atmosphere– Layer of gases that surround Earth. Allows you tobreathe and protects earth.• Lithosphere– Surface of the planet that forms the continentsand the ocean floor.
Earth System (4 physical systems)• Hydrosphere– All the water on Earth (ocean, ice, and watervapor in the atmosphere)• Biosphere– Part of Earth where life exists.
Ocean, Continents, and AtmosphereFormation• All formed because of one major source:
THE EARTH’S HYDROSPHERE• The Earth’s liquid water constitutes thehydrosphere.• The vast majority of Earth’s water is in the oceans(salt water), with smaller, but geologicallyimportant, quantities of fresh water in lakes,rivers, and ground water.• the total mass of Earth’s water is about 300 timesthe mass of the atmosphere.• Without water, which facilitates the formation ofcarbonate rock, the atmospheric content of CO2would be far higher than it is.
Echo Sounders for Measuring Ocean Depths and Floor Profiles
Ocean Facts•The Pacific Ocean is the largest of the fourmain oceans•The Atlantic Ocean is the busiest. Many shipscross the Atlantic, carrying cargo between theAmericas, Africa, and Europe•The Arctic Ocean is the smallest and coldest•The average temperature of all oceans is about39 degrees F (3.8 degrees C)
•Oceans are always moving•Tides change twice a day, all over the world, as the oceansrise and fall along the shoreline. Scientists think this iscaused by the pull of the sun and moon on our earth•Coral Reefs are vast, rocky areas located in shallow, tropicalwaters. They are like the tropical rain forest of the ocean!The greatest variety of plant and animal life in the ocean livethere. Coral reefs are formed from the bodies of small seacreatures called polyps•The worlds oceans contain nearly 20 million tons of gold
“Black Smoker” Under-Sea Volcanic Activity• Under-sea volcanic activity givesrise to high-temperature plumesof water, containing particles ofigneous rock that give rise to theappearance of black smoke.• The boiling point of water underthe high pressures on the oceanfloor can be considerably higherthan at the surface; hence thetemperatures of the volcanicplumes can be much higher aswell.• It has been discovered that somespecies of animal life thrive on theenvironment of these “blacksmokers”, including their very hightemperatures.
• Inner Core –1200 km madeof solid Fe, Ni.• Outer Core –2250 km madeof liquid Fe, Ni.• Mantle – 2900km made ofdense rocks.• Crust – 5 – 40km made ofsolid lighterrocks.Lithosphere (Crust and MOHO)– 100km thick.MOHO = MohorovicicDiscontinuity
Lithosphere and the solid earth: the solid earth lies beneath theatmosphere and the oceans and composes 29% of the earthssurface. It is divided into several distinct units or layers:– lithosphere or crust: two (2) types of crust: oceanic andcontinental with basic differencesOceanicOceanic crust is thinner, denser, and usually darker in colorContinentalContinental crust is lighter in weight, less dense, light incolor, and tends to float over oceanic crust– mantle: beneath the crust; houses molten rock material calledmagma– outer core: composed of liquid iron and nickel; very densematerial– inner core: composed of solid iron and nickel; extremely densematerial
The Crust• This is where we live!• The Earth’s crust is made of:Continental Crust- thick (10-70km)- buoyant (less densethan oceanic crust)- mostly oldOceanic Crust- thin (~7 km)- dense (sinks undercontinental crust)- young
The seven continents:1. Asia2. Africa3. North America4. South America5. Antarctica6. Europe7. Australia