Earth Science Lesson #2 Earth’s Structure Name
Radioactive dating techniques provide data that indicates the Earth was formed approximately
_________________ years ago.
•As the Earth cooled, chemical reactions resulted in the production of the layers of the earth that exist today. These include a _______________ inner and outer core and a _____________ crust and mantle.
•The crust is the outermost layer of the Earth. It is also the ____________ layer and is divided into two types as shown below.
35-70 km thick Up to thick
Up to 4 billion years old or over 3,500 million Up to 200 million years old
Density about Density about 3 g/cm 3
Igneous and sedimentary rocks Igneous rocks like gabbro and basalt
The crust is composed mainly of _________________, oxygen and aluminum.
•The mantle, the __________ layer of the Earth is just below the crust. The mantle has a thin, sedimentary layer of ___________ at the top, but under that is mainly magma.
•Magma is __________ rock from the center of the Earth. The Mantle is hotter and denser because pressure inside the Earth increases with ____________.
•The mantle is composed primarily of iron, ____________, aluminum and silicon.
•The core is nearly _____________ as dense as the mantle because its composition is metal (iron and ____________ ) rather than rocky.
•The core is made of two parts, a liquid outer core and a solid inner core.
•It is thought that the Earth’s magnetic field is created by the spinning of the liquid outer core as the Earth rotates.
Igneous Rock
 Formed at the surface from ___________ or formed inside the crust from __________ that has cooled.
 Examples: granite and basalt
 __________ cooling igneous rock (inside the earth’s crust), allows the formation of
____________crystals of individual minerals. (plutonic/intrusive)
 ______________ cooling igneous rock (outside the earth’s crust) has a ____________ texture with small crystals. (volcanic/extrusive)

Sedimentary Rock
 Formed from ___________ and erosion or from precipitated fragments that have been bound under pressure
 Examples: Limestone or _____________
 Sedimentary rock is the most common source of ______________.
Metamorphic Rock
 Is formed under conditions of extreme temperature and ______________ change.
 Examples: Gneiss and marble
 Note: If too much temperature and pressure exist, the rock will __________ and become igneous.