The Inner Earth Continental Drift Convection Currents, and How Heat Works Chapter 5 Updated January 2012

1.The Earth does not look the same today as it did millions of years ago because it’s surface has been lifted up, pushed down, bent, and broken apart.

2.Scientists use both direct and indirect evidence to study the inside of the earth. Direct evidence- rock samples Indirect evidence- seismic waves through the earth

Rock samples can tell us what the conditions may have been like on Earth when the rock formed. Seismic waves Geologists can measure the speed at which the waves travel through the earth to determine the structure of the planet. Just as you may knock on a wall to find a stud while hanging a picture. It sounds hallow if there is nothing behind it; and solid if there is.

A Journey to the center of the Earth Temperature 5. As you travel toward the center of the earth it gets hotter because you are getting closer to the core, just as you get warmer the closer you get to a camp fire. 6. The center of the Earth is hot because of two reasons: 1. There is leftover heat from the formation of the planet billions of years ago 2. The main reasons is because of radioactive materials decaying in the core. The core is basically a nuclear reactor. Pressure 7. Pressure increases the deeper you go because there is more and more weight on top. If you go down one mile, there is a mile of rock above pushing down.

The Crust 8. The crust is the outer layer of rock that forms the outer skin that includes dry land and the ocean floor. a). The crust beneath the ocean is called the oceanic crust it is made from basalt. b).In most places the crust is between 5 and 40 km thick. It can be up to 70 km thick under mountains.

The Mantle 9.The mantle is made up of very hot rock but solid. It is divided up into layers depending on the physical characteristics of that layer. The mantle is approximately 3,000 km thick. 10.The lithosphere is the uppermost part of the mantle similar to the crust. Approximately 100 km thick. 11.The asthenosphere is the soft part of the mantle just below the lithosphere. 12.The lower mantle is beneath the asthenosphere and extends all the way to the core.

The Core 13. The core consists of two parts, the inner and outer. It is made mostly of the metals iron and nickel. -The outer core is liquid -The inner core is solid Together the core is approximately 3, 486 km thick. The immense pressure does not allow the inner core to become a liquid. The core and the Earth’s magnetic field 14. Scientists believe the earth’s magnetic field is caused by the movements in the liquid outer core.

Convection and the Mantle- Section 2 Lets first discuss what heat is: Heat is the movement or vibration of molecules within a substance. The faster they move the hotter the substance is. It is important to know that heat will always move from warm to cold

Types of Heat Transfer Radiation, Conduction and Convection 16. Radiation- The transfer of heat energy through space. No direct contact with anything. Example: Sun and fire. 17. Conduction- The transfer of heat between objects that are touching. Examples: a spoon in a hot cup of tea. Your hand touching the hot handle of a pot on a stove. 18. Convection- The movement of heat through a fluid (gas or liquid). The movement depends on the temperature and the density of the fluid. Hot substances usually rise and cooler ones sink (Think of a hot air balloon). Examples: Heating water in a pot. Ocean currents. Movement of air through the atmosphere.

Radiation

Conduction

Convection

Convection Currents in the Earth 20. Heat from the Earth’s core cause convection currents in the mantle just like water in a pot on the stove. Hotter substances rise to the surface and cooler ones sink, in this case magma.

Section 3 pages Drifting Continents 21. Alfred Wegener theorized that the continents were once all together and have since drifted apart. 22. This idea he called Continental Drift. 23. He believed that about 300 million years ago all the landmasses were together in one super continent called Pangaea.

Evidence In Support of Wegener’s Idea 24. There is evidence in land features, fossils, and evidence of climate change to support Wegener’s hypothesis. 25. Land Features- Mountain ranges line up and continents seem to fit together.

Evidence Continued 26. Fossil evidence- The fossils of the same plants and animals appear on different continents now separated by oceans.

Wegener also presented some fossil evidence. One was an animal fossil and the other was a plant fossil. Mesosaurus was an aquatic dinosaur closely related to the modern Alligator. Its fossil remains are only found near the eastern side of South America and the adjoining western side of Africa when the two continents are positioned side by side. Hence, Wegener concluded that the best explanation for this unusual occurrence is that the two continents were once joined together (or the same landmass), before Mesosuarus became extinct, until they fractured and drifted away from each other. Opposing scientists argued that there must have been a land bridge linking South America and Africa. But no such evidence for a land bridge across the south Atlantic Ocean has been observed since.

Evidence Continued 27. Climate – As a continent moves toward the poles its climate becomes colder. As a continent moves towards the equator its climate becomes warmer. The continent will bring with it fossils from its previous location. Example: Fossils from tropical plants have been found on an island in the Artic Ocean. This island must have been originally located near the equator. There is also evidence of glaciers on the continent of Africa indicating it was much colder there in the past..

Wegener’s Theory Rejected 28. At the time Wegener could not show evidence of how the continents moved, so his theory was rejected. The scientist at he time believed that mountains formed from the cooling of the Earth. Wegener said that if that was true then there would be mountains all over the Earth. Wegener proposed that mountains formed from the collision of continents. We now know that the continents move by means of convection currents in the mantle.

Sea Floor Spreading Section 4 page In the mid- 1900’s scientists used sonar to map the ocean floor’s topography. They discovered mid ocean ridges which are like mountains on the sea floor. These mountains look like seams on a baseball.

Wow, look at this mid- ocean ridge!

30. In sea-floor spreading, the floor spreads apart along both sides of a mid-ocean ridge as new crust is added. As a result, the ocean floors move like conveyer belts.

Evidence from molten material 31. At the mid ocean ridge, scientists found rocks that look like pillows and as though it has been squeezed from a tube of toothpaste.

Evidence of Sea Floor Spreading 32. The earth has a magnetic field which magnetizes the iron in the molten rock. The rock solidifies recording the north south direction of the earth’s magnetic field at the time. This record shows that the magnetic field of the earth has reversed many times. North / south South/ north 33. Rock samples taken close to the ridge are younger than ones farther away. (Drilling samples)

35. Is the Atlantic Ocean getting wider or narrower? Answer- Wider!

Subduction page The sea floor plunges down in what are called deep ocean trenches. This usually happens at the continental crust.

The Theory of Plate Tectonics Section 5

Plate Tectonics 36. What is plate tectonics? Plate tectonics is the theory that pieces of the lithosphere are in motion. It explains the formation, movement, and subduction of plates. The three types of plate boundaries are:  Divergent boundaries  Convergent boundaries  Transform boundaries

Plate Boundaries Three Types: 37. Divergent- The area where two plates move apart or diverge. 38. Convergent- The area where two plates come together or meet. 39. Transform- The area where two plates move past one another in opposite directions.

Divergent boundary- where two plates move apart, most occur along mid- ocean ridges. Rift valley- when divergent boundaries occur on land

Convergent boundary- A place where two plates come together.

Transform boundary- An area where two plates slip past on another in opposite directions.

Fault- Breaks in the earth’s crust where rocks have slipped past each other.

Can you identify the different boundaries here?