SEDIMENTARY ROCK BIG Idea Most rocks are formed

SEDIMENTARY ROCK

BIG Idea Most rocks are formed from pre-existing rocks through external and internal geologic processes.

The formation of sedimentary rocks begins when weathering and erosion produce sediments…

Weathering: the breakdown of rocks and minerals at or near the Earth's surface into smaller pieces (sediments).

Erosion: the removal and transportation of broken down sediment.

Sediments: rock, minerals and organic matter broken into fragments.

HOW are sediments transported?

Wind Moving water Gravity Glaciers

What happens to sediments after they are transported?

Deposition begins when erosion stops: n the moving particles fall out of the water or wind and settle on a new surface. n sediments get dropped off…

How sedimentary rocks form: 1. 2. 3. 4. WEATHERING EROSION DEPOSITION COMPACTION: air and water is SQUEEZED out of the sediments 5. CEMENTATION: mineral growth GLUES sediment grains together into solid rock

FORMATION OF SEDIMENTARY ROCKS ARE EITHER CLASTIC, CHEMICAL or ORGANIC (BIOCHEMICAL)… n 1. CLASTIC – MADE UP OF FRAGMENTS FROM PRE-EXISTING ROCKS

a. CONGLOMERATE: MADE OF ROUNDED PEBBLES

b. BRECCIA: FRAGMENTS THAT HAVE SHARP AND ANGULAR EDGES

c. SANDSTONE: MADE OF SAND GRAINS CEMENTED TOGETHER

d. SHALE: CLAY-SIZED PARTICLES CEMENTED TOGETHER

• e. Siltstone: another finegrained sedimentary rock

2. CHEMICAL (NON-CLASTIC): ROCK FORMED CHEMICALLY OR ORGANICALLY FROM MINERALS THAT PRECIPITATE (separate) FROM WATER (solution)

EVAPORITE: FORMED FROM MINERALS LEFT AFTER WATER EVAPORATES ROCK SALT (HALITE)

rock gypsum chert (flint)

• 3. ORGANIC (biochemical) – MADE UP OF ORGANISMS coal / peat chalk fossiliferous limestone

coquina

Porosity: percentage of open spaces in a rock or sediment

FACTORS THAT INFLUENCE POROSITY: (a) SORTING: amount of uniformity in particle size HIGH pore space LOW pore space

(b) SHAPE: rounder particles = more porous (c) PACKING: loosely packed = more porous

Permeability: how freely water flows through open spaces in a rock (the pores must be connected) Impermeable – water can NOT flow through

Can something be porous but impermeable? The cork end is red because the wine went into it. Does this mean it is porous? If you turn the bottle upside down will it leak? Is the cork permeable?

SEDIMENTARY ROCK FEATURES 1. STRATIFICATION: LAYERING DUE TO THE CHANGE IN THE KIND OF SEDIMENT

2. RIPPLE MARKS: FORMED BY THE ACTION OF WIND AND WATER ON SAND

3. MUD CRACKS: WHEN MUD DRIES

4. FOSSILS: THE REMAINS OF ANCIENT PLANTS OR ANIMALS