Rocks And The Rock Cycle

What Are Rocks? Rocks are a mixture of one or more minerals as well as mineraloids, glass or organic particles Often several different minerals are mixed together, which gives a rock its color and texture. Often these minerals, mineraloids, glass or organic particles must be put under great pressure or heat.

There Are Three Different Types of Rocks Igneous Rock 2. Metamorphic Rock 3. Sedimentary Rock

Igneous Rocks "Fire Rock"

Igneous rocks are rocks that are formed as molten material cools. They can form underground where magma cools slowly or above ground where lava cools quickly.

There Are Two Types Of Igneous Rock Intrusive Igneous Rock 2. Extrusive Igneous Rock

Intrusive Igneous Rock Intrusive igneous rocks are rocks that are formed when magma cools beneath Earth’s surface. They are found when the rocks and soil that once covered them are removed by erosion. They are also found when forces like compression or tension push molten material to Earth’s surface.

Extrusive Igneous Rock Extrusive igneous rocks are formed by lava that cools on Earth’s surface. The lava is exposed to air and moisture, and it cools quickly. Which igneous rock will have bigger crystals?

Classifying Igneous Rocks Unless you’re near an erupting volcano, we can’t witness the formation of igneous rocks. So how do we know if the igneous rock is intrusive or extrusive?

Look at the size of the crystals in the rock. If it has big crystals it means it cooled slowly If it has small crystals it means it cooled quickly This piece of ryholite cooled quickly on the surface, it has small crystals. This piece of granite cooled slowly below the surface, it has big crystals.

Ways to Define Grain Size There are certain words used to describe the grain size in a rock. Some of the words are: Fine-grained Coarse-grained Glassy Porous

Igneous rocks can also be grouped by their overall color. Light colored rocks must be composed of light colored minerals like quartz or feldspars. Dark colored rocks are composed of minerals like pyroxenes and amphiboles Quartz Pyroxenes

A Little More About Igneous Rocks These rocks are the most abundant type of rocks on Earth. They’ve been classified to make them easier to study. By studying them geologists and other scientists have been able to hypothesize how Earth formed. Kinda big deal? Yeah I think so.

Metamorphic Rocks So you found a rock on the way to school, because you know so much about igneous rocks you are able to classify this as one. Will this rock remain unchanged forever? Can you think of some ways that rocks can change?

Ways That Rocks Change There are different methods that rocks change. Weathering Heat Pressure As well as the other Lets talk about lunch

What Are Metamorphic Rocks? Metamorphic rocks are rocks that are changed by heat or pressure or both.

What Really Happens to Metamorphic Rocks

Basically Rocks under Earth’s surface are put under pressure from the layers above and they are exposed to heat from magma. If these are great enough, the rocks melt and magma forms. If these are not great enough to melt the rocks, mineral grains in the rock may change in size or shape.

This picture is of pebbles that look like normal ones from the front but going to a right hand cut angle the pebbles are longer than expected. This is caused by the pebbles stretching during metamorphism, it became hot enough to behave like plastic and stretch. This is a picture of quartz grains that were probably originally rounded but have been recrystallized under high pressure and temperatures to which caused the grains to grow larger and infringed on each other.

Classifying Metamorphic Rocks Metamorphic rocks that have a foliated texture form when minerals in the original rock flatten under pressure Foliated- texture of metamorphic rocks whos mineral grains have been flattened and lined up in parallel bands

Examples of Foliated Rocks Some examples of foliated rocks include slate which forms from shale.

Some metamorphic rocks the mineral grains change, combine, and rearrange, but do not form visible bands. This is known as non-foliated texture

Difference Between Foliated and Non-foliated Foliated rocks will break easily into layers. Non-foliated rocks will fracture into pieces of random sizes and shapes.

Sedimentary Rocks Where do sedimentary rocks come from? What are the two major processes that change Earth’s surface? Weathering Erosion

Weathering of Rocks The weathering of rocks is when rocks or remains of plants and animals are broken down into smaller pieces called sediments

Erosion of Rocks When rocks are transported by water, wind, ice and gravity. Once they are transported they are deposited somewhere, or dropped off. This rock, Siwash Rock, was once apart of Stanley Park but became separated through the process of erosion and weathering.

What are Sedimentary Rocks? Under certain conditions deposited sediments recombine to form a solid rock.

How do Sedimentary Rocks form? Layer after layer sediments are deposited. As more and more layers form, the pressure they apply to the layers beneath them causes the sediments to compress. This is called compaction.

Classifying Sedimentary Rocks Sedimentary rocks can be composed of any type of weathered and eroded rock material and sometimes even particles from plants and animals. To classify these rocks we must look at the sediment they contain and the way that the rock was formed.

Detrital Sedimentary Rocks These rocks are made of broke fragments of other rocks. The fragments have been compacted and cemented together.

Shale Shale is a detrital sedimentary rock. It requires little cementation to hold its particles together. The sediments are clay-sized minerals which are even smaller than sand-sized particles. These sediments can compact together by pressure from overlying layers. Can you think of another detrital sedimentary rock?

Shale Sandstone

The sediments from detrital rocks come from weather and are transported as solid particles. Does this happen with all sedimentary rocks? Limestone Rock Salt or Halite

Chemical Sedimentary Rocks Some sedimentary rocks come from minerals that were once chemical compounds dissolved in solution. So if these minerals are in solution form how can we get them to be in sedimentary form? Evaporation

Chemical Sedimentary Rocks When the water in lakes and seas evaporates they leave behind the chemical compound in concentrated amounts. What are some of the rocks that can form from this task? Gypsum, rock salt, and limestone are some of the chemical sedimentary rocks!

Organic Sedimentary Rocks What are the materials that sedimentary rocks form from? Fragments of other rocks Chemical compounds Minerals FOSSILS!!!

Organic Sedimentary Rocks Organic sedimentary rocks have large amounts of remains known as fossils. What are fossils? These rocks are classified as organic sedimentary rocks. - One of the most common is limestone which consists mostly of the remains of once living aquatic organisms.

Organic Sedimentary Rocks Ocean animals like mussels and snails make their shells from calcite and other minerals. When they die their shells accumulate on the ocean floor where they can be compacted together and form sedimentary rocks.

Rock Cycle The process by which Earth’s materials change to form different kinds of rocks makes up different kinds of rocks.

Rock Jokes What does a rock want to be when it grows up? A rock star What do you do to a baby rock? --Rock it What do you call a dog who collects rocks? A Rockhound How do rocks wash their clothes? In the Rock Cycle