Transcript III. SEDIMENTARY ROCK

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:
 the moving particles fall
out of the water or wind
and settle on a new
surface.

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
SEDIMENTARY ROCKS ARE
EITHER CLASTIC, CHEMICAL or
ORGANIC (BIOCHEMICAL)…

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