Earth Science Chapter 5

Plate Tectonics

Big Ideas

• Earth’s Interior• Convection and the Mantle• Drifting continents• Sea-floor Spreading• Plate Tectonics

Earth’s Interior

•How far do you think it is to the center of the Earth?

•Almost 4,000 miles!•The deepest mine in the world is only 2 miles

•How do you think scientists know about the center of the Earth?

• Geologists use 2 main types of evidence to learn about Earth’s interior:–Direct Evidence from rock

samples–Indirect evidence from

seismic waves

Evidence from Rocks

• Humans have drilled holes and extracted rock from depths of 12 miles• Blasts from the Earth have

brought rocks from 100 ft to the surface

Evidence from Seismic Waves

• Earthquakes produce seismic waves• The speed of seismic waves

and the path they take show the structure of the planet

Three main layers

• The three main layers of Earth are the crust, mantle, and the core• These layers differ in size,

composition, temperature, and pressure

Temperature

• The first 20 meters beneath Earth’s crust is cool• After this depth, temperature

rises 1 degree Celsius per 40 meters• Heat comes from the molten

layer and radioactive substances

Pressure

•The deeper you go, the higher the pressure•This pressure is equal to that of a swimming pool

Pressure

Lab Skills Activity

• Work with a partner, • Read the directions to the Lab Zone Skills

Activity• Create the Data Table on page 129

Crust• Crust is a layer of rock that

forms Earth’s outer skin• Crust includes both dry land

and ocean floor• Crust is very thin compared to

the other layers of Earth, only 5-70 km thick

Crust

Crust

• The crust beneath the ocean is oceanic crust and usually made of basalt• Continental crust consists of rocks

such as granite

• I was very disappointed in the behavior of some of you on Friday.

• That was extremely disrespectful of you to run from the classroom when the bell rang.

• You need to remember that I dismiss you and not the bell.

• Please take your seat and sit quietly while you wait for class to begin

Mantle

• The mantle is about 40 km below the surface• It consists of a hot, solid rock• It can be divided into layers• The mantle is about 3000 km

thick

Mantle

Lithosphere

• The crust and the uppermost part of the mantle form the lithosphere• It is about 100 km thick• Lithos means “stone” in Greek

Lithosphere

Asthenosphere

• Under increase heat and pressure• Less rigid-soft like tar, but still

solid• Asthenes means “weak” in Greek

The Lower Mantle

• Beneath the asthenosphere the mantle is solid• This material extends to the

Earth’s core

Lower Mantle

The Core

• Consists of mostly nickel and iron• Made of two parts, a liquid outer

core and solid inner core• Together it is about 3486 km

thick

• Despite extreme pressure, the outer core is molten surrounding a dense, solid inner core• Evidence suggests that the extreme

pressure in the inner core will not allow the solid metal to spread and become liquid

Core

Core and Magnetic field

• Scientists think that movements in Earth’s liquid outer core create Earth’s magnetic field.• This magnetism is what attracts a

compass’ needle towards north (it aligns with Earth’s magnetic field)

Individually

• Complete the section 1 assessment on page 131, including the “writing in science” assignment. If you do not complete these in class, they will become your homework and will be due tomorrow.

Make a Chart

Types of Heat Transfer

Radiation

Explanation/definition

Conduction

Explanation/Definition

Convection

Explanation/Definition

When you complete the chart

• Read the sections “Convection Currents”, and “Convection Currents in Earth.”

• 1. Define Convection Currents• 2. Explain how convection currents work,

using a real example• 3. Create an illustration of a convection

current

Drifting Continents

• http://www.youtube.com/watch?v=WaUk94AdXPA

Continental Drift

• Prior to Columbus, mapmakers did not know about the new worlds• Shortly after they began to

notice how the coastlines of several countries seemed to fit together like a puzzle

Continental drift

• Early 1900s German Scientist Alfred Wegener made a hypothesis:• All of the continents were

once joined together in a single land mass and have since drifted apart.

The Origin of Continents and Oceans

• Wegener gathered evidence from different scientific fields to support his ideas about continental drift.• He studied land features, fossils,

and evidence of climate change

Write a Book!

• Make your own version of Wegner’s book• Use the same title as he did• Read pages 138-138 about the evidence he

found• Create a page for each type of evidence• Explain how the evidence supports his

hypothesis and include illustrations if appropriate.

• Page 1: Title• Page 2: Evidence from land

features• Page 3: Evidence from fossils• Page 4: Evidence from climate• Page 5: Conclusion