C HAPTER 6, S ECTION 2 Standards 3c. Students know how to explain the properties of rocks based on the physical and chemical conditions in which they are formed, including plate tectonic properties. Objective 1 Summarize 3 factors that affect whether rock melts. Objective 2 Describe how the cooling rate of magma and lava affects the texture of igneous rocks. Objective 3 Classify igneous rocks according to their composition and texture. Objective 4 Describe intrusive and extrusive igneous rock structures. Assessment End of Section Questions, Daily Quiz, Chapter Test Review Daily Bellwork, Science Starters, Standards Practice

K EY T ERMS Create a flash card for the following key terms (p. 129 in textbook):  Igneous Rock  Intrusive Igneous Rock  Extrusive Igneous Rock  Felsic  Mafic If you finish early, study your flash cards!

I GNEOUS R OCK Most Igneous Rock (formed from cooled magma) is crystalline (made of crystals). Magma forms when rocks melt. 3 Factors determine when rock melts: temperature, pressure, and pressure of fluids in the rock.

I GNEOUS R OCK V IDEO C LIP

P ARTIAL M ELTING Different minerals have different melting points. Minerals with lower melting points, melt first. The process of different minerals in the rock melting at different temperatures is called PARTIAL MELTING.

F RACTIONAL C RYSTALLIZATION When magma cools, the opposite of partial melting occurs: freezing. Different minerals have different freezing points. As some minerals freeze, the composition of the remaining magma changes, creating new minerals. This is called fractional crystallization.

F RACTIONAL C RYSTALLIZATION Crystals that freeze/form early tend to be the largest.

D EMO

T YPES OF I GNEOUS R OCK Magma that cools deep inside the crust Intrusive Lava that cools at the Earth’s surface Extrusive

INTERACTIVE! Create and Acrostic Poem using the word IGNEOUS. I G N E O U S

T EXTURES OF I GNEOUS R OCKS Coarse-Grained Intrusive Large, well-developed mineral crystals Ex.: Granite Fine-Grained Extrusive Small Mineral Grains Grains cannot be seen with human eye Ex: Basalt Other Mixture of large and small crystals Forms as a result of slow cooling at first then rapid cooling. Highly viscous magma that cools quickly results in very few crystals If this magma has little gas=GLASSY If this magma has lots of gases=VESICULAR (holes)

T EXTURES V IDEO C LIP

Q UICK C HECK !! 1. Name the 2 types of Igneous Rock: ____________________________________________ 2. Give an example of a Course-Grained Igneous Rock: ______________________________________

C OMPOSITION OF I GNEOUS R OCKS Mineral Composition of igneous rocks is determined by the chemical composition of the magma from which the rock formed. Three families of igneous rock: Felsic Mafic Intermediate

C OMPOSITION F AMILIES Felsic Rock Forms from Magma that has large amount of Silica. Light coloring Contains feldspar Mafic Rock Forms from Magma that has low amounts of silica and lots of iron and magnesium Dark in color Intermediate Rock Contains less silica than Felsic but more than Mafic

I NTRUSIVE R OCK S TRUCTURES Igneous Rock masses that form underground are called INTRUSIONS. 5 types of intrusions: Batholiths—largest of all intrusions, larger than 100 km squared, form the core of mountains Stocks—same as a batholith but smaller than 100 square km. Laccoliths— “lake of rock”, when magma flows between rock layers and spreads upward into a dome shape. Sills-when magma flows between the layers of rock and hardens. Always parallel to the layers of rock below and above. Dike-Magma that forces itself through vertical fractures and solidifies.

E XTRUSIVE R OCK S TRUCTURES Igneous rock masses that form on Earth’s surface are called EXTRUSIVE ROCK STRUCTURES. Lava from a volcano that cools and becomes rock is an EXTRUSIVE ROCK STRUCTURE.

A NIMATED I NTRUSIVE AND E XTRUSIVE F EATURES

Q UICK C HECK !! 1. What is the difference between Intrusive and Extrusive Rock Structures? ______________________________________________ ______________________________________________ ______________________________________________ 2. What is Felsic Rock? ______________________________________________ ______________________________________________ 3. Name and Define 2 types of Intrusive Rock Structures: ______________________________________________ ______________________________________________ ______________________________________________ ______________________________________________

A SSESSMENT In groups create posters for one of the following: Intrusive Extrusive Course-Grained Fine-Grained Felsic Mafic Intermediate

D AILY Q UIZ