At the planets center lies a dense metallic core. Scientists know that the core is metal because: 1. The density of Earths surface layers is much less than the overall density of the planet, as calculated from the planets rotation. If the surface layers are less dense than average, then the interior must be denser than average. Calculations indicate that the core is about 85% iron metal with nickel metal making up much of the remaining 15%. 2. Metallic meteorites are thought to be representative of the core. The 85% iron/15% nickel calculation above is also seen in metallic meteorites (Figure 1.1). If Earths core were not metal, the planet would not have a magnetic field. Metals such as iron are magnetic, but rock, which makes up the mantle and crust, is not. Scientists know that the outer core is liquid and the inner core is solid because: 1. S-waves do not go through the outer core. 2. The strong magnetic field is caused by convection in the liquid outer core. Convection currents in the outer core are due to heat from the even hotter inner core. The heat that keeps the outer core from solidifying is produced by the breakdown of radioactive elements in the inner core. Click image to the left or use the URL below. URL:
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scientists calculate earths density by using the
a) density of the material in each layer and the volume of each layer. --> b) speed of the planets rotation. c) size of the tides. d) all of the above.
the core is made of
--> a) iron and nickel metal b) peridotite c) gabbro and basalt d) none of these
the core is less dense than the surface layers.
a) true --> b) false
scientists believe that metallic meteorites are representative of the core.
--> a) true b) false
earths magnetic field is caused by
a) convection in the mantle. b) conduction in the mantle. --> c) convection in the outer core. d) conduction in the inner core.
which statement is not true about the core?
a) it is the cause of earths magnetic field. --> b) the inner core causes the magnetic field. c) the inner core is hotter than the outer core. d) p-waves bend as they go into the inner core.
scientists know which layer of the core is liquid and which is solid because
a) s-waves do not go through the inner core b) p-waves do not go through the inner core --> c) s-waves do not go through the outer core d) p-waves do not go through the outer core
which of these help to verify the composition of earths core?
a) metallic meteorites b) density calculations c) the magnetic field --> d) all of the above
seismic waves indicate that the inner core is a solid and the outer core is a liquid.
--> a) true b) false
the core is still extremely hot due to
a) heat left over from earths formation. b) solar energy that travels down from the surface. --> c) radioactive decay. d) none of these.
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