2- 2- Sedimentary rocksSedimentary rocks form from particles called sediments that pile up in layers. These sediments may be small rock fragments or seashells. Sedimentary rocks usually form underwater.

Sedimentary rock

OceanStream carrying sediment

Rock Rock NameName

Type of Type of SedimentSediment

Place of Place of FormationFormation

Sandstone Sand grains Shallow waters near a shore pounded by waves

Shale Clay particles Deep, calm ocean waters; lake bottoms

Limestone Tiny seashells Warm, shallow seas

Common Sedimentary Common Sedimentary RocksRocks

3- 3- Metamorphic rocksMetamorphic rocks are produced when either igneous or sedimentary rocks undergo a change in form caused by heat, pressure, or both.

IgneousRock

Metamorphic

Rock

Sediments

SedimentaryRock

Erosion

Deposition

Solidification

Melting

Burial andCementin

g

Metamorphism

Heat and/or

Pressure

II II Earth HistoryEarth History A- Interpreting Rocks= A- Interpreting Rocks= rocks

contain information about that area's past.

1-1-Sedimentary rocks indicates the area was once covered by water.

2-2-FossilsFossils in sedimentary rocks tell of past life and the environmental conditions

3-3- Horizontally layered sedimentary rocks are easy to interpret. The bottom layers are the oldest, youngest layers are at the top

OLDEST

YOUNGEST

INVASION OF IGNEOUS ROCK

FAULT

INASION OF IGNEOUS ROCK

PRESENT DAY

FOLDED ROCK

B-B-FossilsFossils remains or traces of organisms that lived long ago. 1-1-Fossils form when a dead plant, animal, or footprint in mud, is covered by sediment that later hardens into rock.

a-a-Almost all fossils are found in sedimentary rock

Trilobite

Brachiopod

CephalopodFootprint

C-C-Dating RocksDating Rocks To determine the age of rocks, scientists use a technique called

1~1~RadioactiveRadioactive datingdating.a.a. Rocks contain small amounts of

radioactive substances that change (decay) into non-radioactive substances at a definite rate. b. b. Using this technique, scientists have been able to assign dates to the Earth. c. c. Earth itself is about 4.5 billion years old.

2-2-Relative DatingRelative Dating:: Section of sedimentary rock oldest sediment is on the bottom and the youngest is on the top.

aa. It only tells us that one fossil is older than another.

Trilobite is an index fossil tells Trilobite is an index fossil tells about the age of the rock layer .about the age of the rock layer .