Earth’s Internal Processes Section 3 Earth’s Interior

Inside the Earth Scientists learn about the interior by: Drilling a hole 200 m into the oceanic crust Studying the behavior of seismic waves Earth’s interior is not the same throughout Earthquake waves arrive at different times

Earthquake Observations A boundary that marks a density change between layers is called a discontinuity.

Think – Pair - Share Why do you think that scientists attempted to drill through oceanic crust instead of continental crust?

Earthquake Observations Seismic recording stations like ours record seismic wave data. Waves refract when they encounter sharp changes in density.

Shadow Zones P- and S- waves spread out from an epicenter Waves travel through 105 degrees of arc Shadow Zone – “dead zone” between 105 and 140 degrees From 140 to 180 degrees only P-waves are recorded

Earth’s Interior 3 Shadow Zones

Earth’s Core Shadow zones reveal A layer in the interior may be absorbing waves S-waves turn into P- like waves S-waves travel only through solids Outer core may be a liquid

Inner Core P-waves are refracted as they pass through the inner core Inner core must be denser than outer core Pressure of outer core keeps the inner core solid Outer core remains liquid because of the high temperatures

Composition of Layers Layers become denser with depth Lithosphere – crust & upper mantle Rocky materials – mostly silicates Asthenosphere – weaker layer under lithosphere Plasticlike layer Mantle – divided into upper and lower Made of silicates

Composition (con’t) Core – divided into outer and inner Mostly nickel and iron Earth may have formed from meteorite- like material Material was forced together by gravity and melted Densest materials are in the core, less dense ones float on the surface

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Post PowerPoint What do scientists know about Earth’s interior? How do they know this?

Question 1 Answer Section Check What is Earth’s core made of? Earth’s core is primarily made of metallic material such as iron and nickel.

Question 2 Section Check Earth’s internal layers become _______ with depth. A. cooler B. darker C. denser D. lighter

Section Check Answer The answer is C.

Question 3 Answer Section Check Why can’t S-waves penetrate the liquid outer core? Answer S-wave only travel through solids. This suggests that the outer core is in a liquid state.