Transcript Sedimentary Rocks

Warm-Up
Thursday, September 20
 Obsidian
is an igneous rock with no
crystals, what type of igneous rock
is it (extrusive or intrusive) and how do
you know?
Extrusive –
no crystal
formation –
cooled quickly
What’s going on now?
Activator
“The President’s Mountain’ is an iconic National
Monument of the USA. The size of the four figures
is awe inspiring. Each President's head is equal to
the height of a 6-story building! The sculptures
were created by using dynamite to blast away tons
of rocks. Jackhammers, wedges, drills, and other
tools were used to finish the job. The rock of Mt.
Rushmore consists of fine-grained granite rock. This
is one of the reasons it was chosen for the
monument, because of granite’s relatively soft,
grainy consistency. Also, granite is resistant to
erosion. The Mount Rushmore National Memorial
took 14 years to complete. It was completed in
1941 and cost nearly 990,000 dollars to construct.”
Mt. Rushmore Creator
Geologists estimate that the
granite at Mount Rushmore
National Memorial will erode only
1 inch every 10,000 years.
He used MATH to determine the
ratio of 1:12.
1 inch model: 1 foot on mountain
To transfer measurements from the
model to the mountain, workers
determined where the top of the head
would be, then found the corresponding
point on the model. A protractor was
mounted horizontally on top of the
model's head. A similar, albeit 12 times
larger, apparatus was placed on the
mountain.
Sedimentary Rocks
Origin
 Sediments
are deposited
 Sediments become compacted and
cemented together
 Usually has layers called strata
The highest layer has
the least pressure.
The lowest layer has
the most pressure.
Deposition— Sediment is dropped
into a new place
 Sediment
deposited in layers
What is Compaction?
1. Layer upon layer of
sediments build up
2. pressure from upper
layers push down on the
lower layers.
What is
Cementation?
1. Water dissolves minerals in soil and
rock.
2. Mineral water flows between
sediments
3. Mineral water crystallizes and sticks
sediments together
Luck of the Draw
 Explain
how sedimentary rocks are
formed. Begin with the first step,
weathering.
Student sitting in
seat 35.
Stratification
Classification

Sedimentary rocks are classified
into _____ types:
1. Clastic Sedimentary Rocks
2. Chemical Sedimentary Rocks
3. Organic Sedimentary Rocks
How?
By the way how are they
classified?.
1. Clastic Sedimentary Rock
 Made
from broken
other rocks.
 Classified
shape
fragments of
by grain size and
Shale
Sandstone
Conglomerate
Circular Fragments
Angled
Fragments
Breccia
Conglomerate
2. Chemical Sedimentary Rock
 Formed
from minerals crystallizing
out of a solution
 The solution is made of minerals and
water.
Halite (Rock Salt)
stalactite/stalagmite
3. Organic Sedimentary Rock
 Rocks
formed from once-living
(organic) things.
Ocean animals called coral
create huge deposits of
limestone. As they die, their
skeletons collect on the ocean
floor.
Organic Limestone
Coquina
 Coquina
rock is a mixture of these
small marine clams, crushed oyster
shell, mollusk shell, fragmented
fossils, fragmented coral, crinoids,
limestone, red sand, white sand,
phosphate, calcite, and perhaps a
little clay.
Coal
A natural dark brown to
black graphite-like material
used as a fuel, formed from
fossilized plants and
consisting of shapeless
carbon with various organic
and some inorganic
compounds.
Stratification (Strata Layers)
 The
process in which sedimentary
rocks are arranged in layers.
The Grand Canyon
The Grand Canyon
Providence Canyon, GA
Cloudland Canyon, GA
Science Terms to Know
Sedimentary & Metamorphic Rocks
1. Strata
2. Stratification
3. Sediment
4. Clastic sedimentary rock
5. Organic sedimentary rock
6. Chemical sedimentary rock
1.
As a group, classify the
sedimentary rocks on
your table by how they
were formed.
2.
As a group, classify the
sedimentary rocks on
your table by grain size.