IGNEOUS R

OCKS

BY: MRS. J

COUCH

WHAT DOES IGNEOUS MEAN?Igneous means “fire” in Latin.

HOW DO IGNEOUS ROCKS FORM?Begin as magma; cools; and becomes a solid igneous rock

WHAT IS MAGMA AND HOW DOES IT FORM?Magma is hot, liquid rock.Forms when:-rock is heated-pressure is released-rock changes composition

WHAT HAPPENS TO MAGMA WHEN IT COOLS AT DIFFERENT RATES? (WHAT DETERMINES AN IGNEOUS ROCK’S TEXTURE?)More time to cool: (slow cooling magma)

-crystals have time to grow larger

-coarse texture (can see crystals in rock)

Less time to cool: (quickly cooled lava)

-crystals don’t grow

-fine grained (almost can’t see crystals or no crystals)

Felsic- light colored igneous rocks that are less dense

Mafic-dark colored igneous rocks that are more dense

HOW DO INTRUSIVE ROCKS FORM?-Magma pushes (intrudes) into

rocks below Earth’s surface and cools

-Usually coarse grained (cools slowly with large, visible crystals)

-Ex. Stone Mtn. (a batholith-the largest of all igneous intrusive rocks)

WHAT ARE THE CHARACTERISTICS OF EXTRUSIVE ROCKS?-Magma erupts (extrudes/exits)

onto Earth’s surface-Common around volcanoes-Lava cools quickly on Earth’s

surface-Very small or no crystals

EXAMPLES:CAN YOU TELL WHICH ONE IS INTRUSIVE AND WHICH ONE IS EXTRUSIVE?

WHERE CAN LAVA COME TO THE SURFACE OF THE EARTH?

-Volcanoes erupt-Fissures-long cracks in Earth’s crust on ocean floor and on dry land