Sedimentary Rocks

• form from pieces of other, existing rocks or pieces of once living things called sediments

• form a thin layer over 75% of Earth’s surface

Lithification

is the process that converts sediments into rock. It is a five step process that begins with weathering.

Weathering → Erosion → Deposition → Compaction → Cementation

Lithification is a VERY slow process.

WeatheringWeathering ONLY occurs on the surface!

Weathering is a chemical or physical process in which rocks are worn down by water, wind, ice, gravity, and organisms.

There are two types of weathering, mechanical and chemical.

Erosion

The second step in the lithification process is erosion, in which sediments and organic material are moved by water, wind, ice, gravity and sometimes even organisms.

DepositionThe now weathered and eroded pieces of sediment are deposited or dropped off somewhere else on the Earth’s surface.

The Law of Superposition states that if the layers of sediment are not disturbed, the oldest rock will be at the bottom and the youngest on top.

Compaction

This is the process in which layers of sediment that have built up over time are pressed and squeezed together.

Cementation• the last step in the lithification process• mineral crystals “glue” sediments together

and give the rock its color

Size of Sediment = Type of Rock

Clastic Sedimentary

• Made from pieces of other rock

• Conglomerate (top) has rounded sediment

• Breccia (bottom) has more angular sediment

Clastic Sedimentary

• Sandstone (above) is made from grain-sized sediment

• Shale (top right) and Mudstone (bottom right) are made from clay and silt sized sediment

Organic Sedimentary

• made from remains of plants and animals

• Chalk (top) is made from grains of tiny sea creatures.

• Limestone (middle) is made from coral reefs and other marine material.

• Coal (bottom) is made from decayed plant material.

Chemical Sedimentary• form when minerals

come out of solution (precipitate) or are left behind after evaporation

• Halite (top) is rock salt created from salt water.

• Limestone (middle) is made from precipitated minerals.

• Geodes (bottom) are made from minerals that crystallize inside a hollow space.

Gemstone Formation

Gemstones associated with sedimentary rock include jasper, malachite, opal and zircon.

Unique Features

Stratification – visible bands that result from layers of different sediment being deposited one atop another.

The oldest layers are always at the bottom. This is the Law of Superposition.

Zhangye Danxia Landform: Gansu, China 20 million years old

Unique Features - Fossils

Petrified Forest National Park, Nevada

Petrified Wood, Nevada

Stonehenge, England(sandstone - clastic)

Arches National Park, Utah(banded sandstone - clastic)

The elephant rock formation in Valley of Fire State Park in

Nevada is natural sandstone (clastic)

Wulingyuan Scenic Area in Zhangjiajie, China is a 100 square mile area containing thousands of sandstone pillars described as nature's version of skyscrapers. Some are taller than the Empire State Building! (clastic)

Koekohe Beachon South Island, New Zealand

Maori legend has it that the Moeraki Boulders scattered along the beach are the remains of eel baskets, gourds, and sweet potatoes from a large canoe wreck.

Scientifically, the spherical rocks are the result of a natural process known as concretion, where grains of sand and stone combine to form these masses. Reaching a diameter of up to six feet, these boulders dot the eroded Otago coastline. (clastic)

12 Apostles in Australia (clastic)

Smithsonian Institution, Washington, DC(sandstone - clastic)

Tasmania's Maria Island includes the swirling, Triassic-era limestone of the Painted Cliffs. (clastic)

Bryce Canyon Utah is made of layered red and orange rock pillars, known as hoodoos. (clastic)

White Cliffs of Dover, England(organic)

Guadalupe Mountain, Texas(organic limestone)

Irish Peat Bogs

Irish Cottages were/are heated with peat.

Peat Bricks

The Blue Grotto, Capri, Italy (organic)

The Blue Grotto

The blue coloration is due to light reflection off of the limestone formations below the water of the grotto.

Bonneville Salt Flats, Utah (chemical)

Salar de Uyuni in Bolivia is the largest salt flat in the world. When dry, the flat is a perfectly horizontal sheet of hexagonal salt tiles. During the wet season, the shallow lake perfectly mirrors the sky, creating an illusion of infinity. (chemical)

lowest point in the U.S. at 282 feet below sea level. (chemical)

The Badwater Salt Flats in California

Caves(chemical limestone)

Striped Icebergs! Are these sedimentary rocks?