Before students can begin to study about the properties of the Long Island Sound, they need to have a knowledge of how the Earth is structured. Through study during earthquakes, scientists have been able to learn alot about the structure of the Earth. Scientists have been able to identify three main zones according to their densities: the thin outer crust, the mantle, and the core in the center.
The
core
and
mantle
lie deep within the Earth’s crust. The
mantle
is about 1,740 miles thick and is made of rock. The central zone of the Earth is called the
core
. It is divided into inner and outer zones. The inner core is solid, but the outer core is liquid. Both are very dense and hot and consist of mainly nickel and iron.
The
mesosphere
is the layer that sits upon
the top of the core and is very hot. The
asthenosphere
is the layer beneath the lithosphere which is in a “plastic” state, so that it behaves like an extremely thick liquid. The
lithosphere
is the upper layer of the Earth. It includes the crust and the top, brittle part of the mantle. This layer can be up to 186 miles thick. The
hydrosphere
is the water (mainly the oceans and seas) on the Earth’s surface.
The Earth’s
crust
is divided into two parts:
oceanic crust
and
continental crust
. The thicker continental crust can vary from about 22 miles thick to as much as 31 miles beneath mountain ranges. This crust is made mostly from pale, granite-like rocks. The oceanic crust is less thick and is formed from volcanic activity. The main elements that make up the crust are: oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium.
To demonstrate the structure of the Earth to your students, you can recreate a picture and label it. Another activity could include building a model of the Earth’s structure with your class. Using different colors of clay, recreate by molding each different color as a different layer. After layering the clay around each other, carefully slice out a chunk from the crust to the inner core. Take out the chunk and the different layers of clay should grant the students with a visual representation of the Earth’s structure. Make sure to provide a chart or key for the different colors and what they represent. Keep this model on display for the children to look at.(see figures 1 and 2 in the appendix for a visual representation of the structure of the earth)