Download Ch 5 S 1 Earth`s Interior

Chapter 5: Plate Tectonics
Section 1: Earth’s Interior
1. Exploring Inside Earth
a. Geologists cannot dig to the center of the Earth
i. The conditions are extreme
ii.More than 6000 km to reach the center
iii. Geologists have used 2 main types of evidence to
learn about Earth’s interior
1.Evidence from rock samples
a.Rocks from inside Earth give clues about
Earth’s structure
b.Geologists have drilled holes up to 12 km
i. The drills bring up samples of the rock
c.Geologists can make inferences about
conditions deep inside Earth
d.Forces inside Earth sometimes blast rock to
the surface from more than 100 km deep
2. Evidence from seismic waves
a.Seismic waves: vibrations that travel through
Earth carrying the energy released during an
earthquake
b. Geologists study how seismic waves travel
through Earth
i. Their speed and paths reveal Earth’s structure
a.Now we know the Earth is made up of layers
2. A journey to the center of Earth
a. The 3 main layers are the crust, the mantle, and the core
i. They vary greatly in size, composition, temperature,
and pressure
b. Temperature
i. As we begin to tunnel to the center, we go through cool
rock
ii.At about 20 meters down the rock is getting warmer
iii.For every 40 meters from that point, the temperature
increases 1°C
iv.After several tens of kilometers, the temperature
increase slows.
v.The high temperatures are the result of heat left over
from the formation of Earth
iv. Radioactive substances also release energy inside Earth
c. Pressure: results from a force pressing on an area
i. Inside Earth, pressure increases as you go deeper
because of the weight of the rock above
3. The Crust: the layer of rock that forms Earth’s outer layer
a. Layer of solid rock that includes both dry land and ocean floor
i. Includes rocks, mountains, soil, and water
b. Much thinner than the layer below it
c. Thickest under high mountains and thinnest beneath the ocean
d. Mostly between 5 and 40 km thick
i. Can be up to 70 km
e. The crust beneath the ocean is called oceanic crust
i. Consists mostly of basalt
1.Basalt: dark rock with a fine texture
f. Continental crust forms the continents
i. Consists mostly of rocks such as granite
1. Granite: a rock that usually is a light color and has a coarse
texture
4. The Mantle: a layer of hot rock
a. Made up of rock that is very hot, but solid
b. 3,000 km thick
c. Divided into layers based on the physical characteristics of
those layers
i. The Lithosphere
1.Uppermost part of the mantle
2.Very similar to the crust
3.Lithos means “stone”
4.About 100 km thick
ii. The Asthenosphere
1. Below the lithosphere
2. Less rigid than the rock above
3. Somewhat soft like road tar heated by the sun
4. Asthenes means “weak”
5. Solid
iii. The Lower Mantle
1.Beneath the asthenosphere
2.Extends all the way to Earth’s core
iv. The Core
1. Made mostly of the metals iron and nickel
2. Consists of two parts—a liquid outer core and a solid inner
core—together 3,486 km
a. Outer Core: a layer of molten metal that surrounds the inner
core
i. Liquid
b. Inner Core: a dense ball of solid metal
i. Extreme pressure squeezes the atoms of iron and nickel
so much that they cannot spread out and become liquid
1.The core and Earth’s Magnetic Field
a.The movements in the liquid outer core may
create Earth’s magnetic field
b.Earth acts like a giant bar magnet
c.Compasses align with Earth’s magnetic field
Review
• What causes seismic waves?
Review
• What is the main type of rock in oceanic crust?
Review
• What is the asthenosphere?
Review
• What is the main difference between the inner core and the
outer core?