The document summarizes the different layers that make up the Earth's structure. It describes the crust, mantle, and core in 3-4 sentences each. The crust is the topmost solid rock layer that makes up 0.5% of the Earth's mass. Below is the mantle, which is thicker and denser than the crust and comprises 10% of the Earth's mass. The innermost layer is the core, which is primarily composed of iron and nickel and can be divided into a solid inner core and liquid outer core.

2.  The crust of the earth is very slowly growing
thicker. Volcanic activity is continually
adding mass to the crust. Though the crust is
solid it is.

3.  The crust is about 0.5 % of the earth’s total
mass.
 The crust is made up of silicate rocks such as
granite and basalt.

5.  Oceanic crust - The crust under the oceans
is about 10 km thick and is generally made
up of rock rich in iron and magnesium. These
are primarily basalt formed by volcanic
action at the mid ocean ridges. The oceanic
crust is denser than continental crust.

6.  Continental crust (continental cratons) -
Where there are continents the crust is about
30 to 50 km thick. It is made up of igneous,
metamorphic, and sedimentary rocks. The
continental crust is less dense than the
oceanic crust.

8.  Largest layers of the Earth.
 Much less is known about the mantle than
the crust. The crust we can see, measure,
dig and drill. The mantle is different. We
have little direct contact with the inner
earth. We can tell some things about the
mantle by studying volcanoes and what
comes out of them.

11.  Is made up of rocks rich in magnesium and
iron.
 It is about 400 km thick and is much denser
than the crust.
 It comprise 10% of the earth’s mass

13.  It is more dense and contains a greater
amount of iron than the upper mantle
 It is about 1900 km thick
 It makes up 41% of the earth’s mass

15.  The core is composed primarily of a nickel-
iron alloy. There is an outer core that is
liquid and an inner core that is solid.

18. Inner and Outer core

19.  Outer core is about 2100 km thick. It makes
up about 30 % of the Earth's total mass.

20.  Inner core is about 1300 km thick. It makes
up about 2 % of the Earth's total mass.