Planet Earth
Section 1
Key Ideas
〉 How is Earth’s interior structured?
〉 How has the appearance of Earth changed over time?
〉 What geologic features are common near tectonic plate
boundaries?
Planet Earth
Section 1
To Start…
A peach can be used as a model for some aspects of
Earth’s structure. Compare the drawing of the cross section
of the peach below with the cross section of Earth, and
answer the following questions.
Planet Earth
Section 1
To Start…
1. Describe the outer layer of the peach (the skin).
What aspect of Earth’s structure does the outer
layer of the peach represent?
2. The peach pulp is the next layer.
How would you describe it? What aspect of Earth’s
structure does the peach pulp represent?
3. The pit is the innermost part of the peach.
What is the pit like? What aspect of Earth’s
structure does the peach pit represent?
Planet Earth
Section 1
What is Earth’s Interior Like?
〉 How is Earth’s interior structured?
〉 Earth’s interior is made up of several distinct
compositional layers.
• crust: the thin and solid layer of Earth above the
mantle
– made of hard, solid rock
– topmost layer of Earth
– 1% of Earth’s mass
Planet Earth
Section 1
What is Earth’s Interior Like?
• Oceanic Crust:
– 5-8km, thinner
– more dense than continental
– usually made of basalt
• Continental Crust
– 20-40km, thicker– deepest beneath high
mountains
• 70km in some places
– less dense
Planet Earth
Section 1
What is Earth’s Interior Like?
• mantle: the layer of rock between Earth’s crust and
core
– Almost 2900km thick
– makes up
• 67% of Earth’s total mass
• 80% of Earth’s total volume
– Unsure what it is really like
• Infer it’s composition/consistency from
earthquakes and volcanoes
Planet Earth
Section 1
What is Earth’s Interior Like?
• Earth’s interior gets warmer with depth.
• Earth’s core is nearly as hot as the surface of the sun.
– Earth’s core is composed mainly of nickel and iron.
– The inner core is thought to be solid and metal.
– The outer core is thought to be made of liquid metal.
• core: the center part of the Earth below the mantle\
– 16% of Earth’s volume
– 33% of Earth’s mass
Planet Earth
Section 1
What is Earth’s Interior Like?
• core: the center part of the Earth below the mantle
– Iron/nickel
o Inner Core
o Solid metal, pressure is so great that the atoms are
forced together as a solid despite heat
o Outer Core
o Liquid metal, remains liquid due to the intense
pressure due to the weight of the mantle and crust
Planet Earth
Section 1
Visual Concepts: Structure of the Earth
Planet Earth
Section 1
Visual Concept: Formation of Earth’s Crust,
Mantle, and Core
Planet Earth
Section 1
What is Earth’s Interior Like? continued
• Radioactivity contributes to high internal temperatures.
– The breakdown of radioactive isotopes uranium,
thorium and potassium give off energy that
contributes to Earth’s high internal temperatures.
– Temperatures in the mantle can reach more than
1250 °C.
– The core may reach temperatures above 5000 °C.