Figure 2—The earth with a segment removed to show supposed internal zones.
Crust (6-30 miles) Mantle (1800 miles) Outer core (1400 miles) Inner core (750 miles)
WHAT IS CORE?
The core is the innermost zone of the earth. It is mainly iron with some nickel and cobalt. The inner core probably is solid, but the outer core may consist of the same elements in a molten form. The core is the most dense (heaviest) of the three zones.
HOW DOES THE MANTLE DIFFER FROM THE CORE?
The mantle, which surrounds the core, is a rigid zone of materials rich in iron and magnesium. These materials are not as dense as those found in the core.
WHAT IS THE CRUST OF THE EARTH AND HOW IS IT DISTINGUISHED FROM THE MANTLE AND THE CORE?
The crust, the top part of which includes the ground we walk on, is the hard, outer surface layer of the earth. Although the crust is about 6 to 30 miles deep, the scale (size) of [figure 2] allows it to be drawn only as the thin outer line. The rocks and minerals that we are all acquainted with are found in the crust. These rocks are not as dense and do not have as high an iron content as do the rocks of the mantle and the core.
WHAT IS THE EARTH’S CRUST UNDER ILLINOIS MADE OF?
The earth’s crust under Illinois is made of: sedimentary rocks deposited by water, wind, or glaciers (limestone, sandstone, shale, glacial drift); igneous, or melted rocks (granite, gabbro); and metamorphic, or altered sedimentary and igneous rocks (quartzite, gneiss). These various types of rocks have a relatively thin covering of broken or weathered material called mantle rock and soil.