Igneous RocksIgneous Rocks

States that in a series of rock States that in a series of rock layers, the layers toward the layers, the layers toward the

bottom had to be laid first and bottom had to be laid first and were therefore older than were therefore older than

layers higher up.layers higher up.

What is?What is?

Principle of superpositionPrinciple of superposition

Because they believed that simple Because they believed that simple fossils came before complex &fossils came before complex &

Rocks containing similar fossils must Rocks containing similar fossils must have similar ages even if they are have similar ages even if they are horizontally far aparthorizontally far apart

Linked fossils together in a “guide Linked fossils together in a “guide fossil”fossil”

What areWhat are

Index fossilsIndex fossils

This is molten rock found beneath the This is molten rock found beneath the surface of the earth.surface of the earth.

What isWhat is

MagmaMagma

This is molten rock found above This is molten rock found above the earth’s surface.the earth’s surface.

What isWhat is

LavaLava

This rock forms when molten rock This rock forms when molten rock solidifies above the earth’s surface.solidifies above the earth’s surface.

What isWhat is

Extrusive RocksExtrusive Rocks

This is formed when molten This is formed when molten rock solidifies after squeezing rock solidifies after squeezing into other rocks or intruding into other rocks or intruding

into theminto them

What isWhat is

Intrusive RocksIntrusive Rocks

Intrusive rocks can eventually appear Intrusive rocks can eventually appear at the earth’s surface becauseat the earth’s surface because

What isWhat is

ErosionErosion

Magma that intrudes into cracks that Magma that intrudes into cracks that cut through existing layers of rock cut through existing layers of rock

hardens to form what?hardens to form what?

What isWhat is

dikesdikes

This rock is similar to scoria but is a This rock is similar to scoria but is a light-colored rock. It often contains light-colored rock. It often contains so many trapped bubbles that it can so many trapped bubbles that it can

float in water.float in water.

What isWhat is

PumicePumice

This “natural glass” made of lava cools This “natural glass” made of lava cools rapidly and has no crystals. It occurs rapidly and has no crystals. It occurs

in the colors black, brown, and red in the colors black, brown, and red and it fractures conchoidallyand it fractures conchoidally

What isWhat is

ObsidianObsidian