Internal Earth Evidence Scrapbook

Print, cut out and glue these pictures and images to answer the questions from your INTERNAL EARTH STRUCTURE REVIEW QUESTIONS

P-waves will travel through solids and liquids, s-waves only go through solids The timing of the arrival of seismic waves from earthquakes indicates increasing density of the rock toward the center of the planet.

Disappearance of s-waves indicates a liquid outer core of the Earth

 Earthquakes Help Take Deep Earth's Temperature
Christine Dell'Amore
for National Geographic News

March 29, 2007
New high-resolution seismic images have produced the best estimate to date of the temperature of Earth's extremely deep interior, researchers report.

Reporting in tomorrow's issue of the journal Science, the team calculated that the temperature of the region is 3,950 Kelvin, plus or minus 200.

This translates to a fiery 6,650 degrees Fahrenheit (3,677 degrees Celsius)—which is actually lower than previous predictions.

Van der Hilst's team studied data from earthquake-prone areas of Central America.

The regions are among the few in the world where a large number of quakes occur close enough to seismographic stations for scientists to record earthquakes' seismic waves bounced back from the core.

The researchers compiled data from thousands of earthquakes recorded at more than a thousand stations to create a detailed 3-D map of the core-mantle boundary.

Using this map, the team then estimated the temperature based on two key factors: pressure and mineral content.

For instance, scientists already knew the temperature at which a mineral in the mantle called pervoskite transforms into a high-pressure material called post-pervoskite.

The transition takes place in the lowermost mantle, just above the core, the new data suggested. This in turn provided a correlating temperature for the core-mantle boundary.

The reflection, refraction and increase in speed of p-waves that travel through the center of the planet indicates a solid inner core to the planet
Half of the meteorites that fall to Earth are composed of iron and nickel, and if meteorites are a sample of what the inner planets are made of, then the Earth must contain a lot more iron than is found at the surface.

The density of the entire planet, determined from its gravity and size, is much higher than the density of the rocks we can examine at the surface. This difference between the density of the entire planet and the density of the crust indicates the core must be as dense as iron.
Although it makes a fascinating story, it is not possible to journey to the center of Earth. Instead, scientists gather observations at the surface to construct models of Earth's internal structure. They analyze seismic data—information from earthquakes—to infer processes that occur inside the planet.