1. Igneous Rocks: rock formed when magma or lava cools & hardens
Igneous comes from the Latin word ‘ignis’ which actually means fire. Igneous rocks are a word used for rocks that have formed by the cooling and hardening of molten lava or magma. The atoms and molecules of melted minerals are what make up magma.
The upper section of the Earth’s crust is made up of around 95% igneous rock
There are over 700 different kinds of igneous rocks that have been identified so far.
their minerals and global chemistry gives information about the composition of the mantle

2. Igneous Rocks Extrusive Rock: Formed from lava that erupts from
volcanoes then cools
and hardens on Earth’s surface

3. Igneous Rocks Extrusive Rock: Formed from lava that erupts from
volcanoes then cools
And hardens on Earth’s surface
glassy
Igneous rocks formed on the surface cool down in just a matter of a few hours. The crystals in these rocks can be microscopically small.
Minerals are
not organized
into crystals.

4. 9. Obsidian rocks are igneous rocks that form when lava cools quickly above ground. Obsidian is actually glass and not a mixture of minerals. The edges of this rock are very sharp. Since the Stone Age, people have used obsidian to make cutting tools and tips for their arrows and spears.

5. scoria
pumice
Scoria forms when magma containing abundant dissolved gas flows from a volcano or is blown out during an eruption. As the molten rock emerges from the Earth, the pressure upon it is reduced and the dissolved gas starts to escape in the form of bubbles. If the molten rock solidifies before the gas has escaped, the bubbles become small rounded or elongated cavities in the rock. This dark-colored igneous rock with the trapped bubbles is known as scoria.The red variety of scoria (it also comes in black) is commonly used as landscaping pebbles at Taco Bell. Landscapers know this rock as lava rock.
Pumice is a froth of felsic volcanic glass. It is rock foam with so much air in its structure that it often floats on water. Close examination of fresh pumice shows its glassy nature. Older, weathered pumice looses its glassy appearance. Pumice is an unusual, lightweight rock formed when molten rock is rapidly blown out of a volcano, forming bubbles as it quickly loses pressure and cools at the same time.

6. Extreme close up of pumice shows it’s glassy appearance.

7. Igneous Rocks Extrusive Rock: Formed from lava that erupts from
volcanoes then cools
And hardens on Earth’s surface
glassy
Fine-grained
Minerals are
not organized
into crystals.
Crystals are too
small to be
seen without
a microscope

8. basalt
Basalt forms when lava cools quickly. Most of the ocean floor and the Hawaiian Islands are made of basalt. It is also found on the Moon, Venus and Mars.  Because it is a common rock and very hard, people used basalt for early choppers and for grinding stones to grind grains like millet and barley. Roman engineers paved a lot of Roman roads with basalt, and today engineers still use a lot of ground-up basalt to make asphalt to pave roads. The ocean floor is normally made out of basalt rock
rhyolite

9. The Giant’s Causeway, in Ireland, was made from a lava flow that erupted over 55 million years ago. The lava cooled, and as it did this it split and formed about 40,000 basalt pillars, which look like humongous stepping stones that reach out into the ocean

10. Igneous Rocks Intrusive Rock: Formed from magma that cools and hardens
inside the Earth
There are places on Earth that are so hot that rocks melt to form magma. Because magma is liquid and usually less dense than surrounding solid rock, it moves upward to cooler regions of the Earth. As the magma loses heat, it cools and crystallizes into an igneous rock.
When a liquid cools to a solid, the substance is said to have crystallized. This means as magma cools, the elements in the magma form solid bonds with their neighbors in a repetitive pattern. The minerals form into bigger and bigger crystals until they smash into other crystals. Once enough mineral crystals smash together so hard that they can't be taken apart, the minerals have formed into an intrusive igneous rock. A great example of this type of rock is granite.
Igneous rocks that form deep within the Earth’s crust where temperatures are very high might take thousands of years to cool down. This causes the crystals to be much larger, such as in the case of granite

11. Igneous Rocks Intrusive Rock: Formed from magma that cools and hardens
inside the Earth
Course
grained
There are places on Earth that are so hot that rocks melt to form magma. Because magma is liquid and usually less dense than surrounding solid rock, it moves upward to cooler regions of the Earth. As the magma loses heat, it cools and crystallizes into an igneous rock.
When a liquid cools to a solid, the substance is said to have crystallized. This means as magma cools, the elements in the magma form solid bonds with their neighbors in a repetitive pattern. The minerals form into bigger and bigger crystals until they smash into other crystals. Once enough mineral crystals smash together so hard that they can't be taken apart, the minerals have formed into an intrusive igneous rock. A great example of this type of rock is granite.
Igneous rocks that form deep within the Earth’s crust where temperatures are very high might take thousands of years to cool down. This causes the crystals to be much larger, such as in the case of granite
Larger crystals
all roughly the
same size

12. granite
diorite
pegmatite

13. Igneous Rocks Intrusive Rock: Formed from magma that cools and hardens
inside the Earth
Porphyritic
Course
grained
Large crystals
are scattered
on a back-
ground of
small or
microscopic
crystals
some crystals started to form before others and had therefore more time and room to grow.
Larger crystals
all roughly the
same size

14. andesite
porphyry

15. Igneous Rocks Extrusive Rock: Formed from lava that erupts from
volcanoes then cools
And hardens on Earth’s surface
Intrusive Rock:
Formed from magma that
cools and hardens
inside the Earth
glassy
Fine-grained
Porphyritic
Course
grained
Large crystals
are scattered
on a back-
ground of
small or
microscopic
crystals
Minerals are
not organized
into crystals.
Crystals are too
small to be
seen without
a microscope
Larger crystals
all roughly the
same size

16. compacting and cementing
Sedimentary Rocks:
Rock formed from the
compacting and cementing
of sediment
made when sand, mud and pebbles get laid down in layers. Over time, these layers are squashed under more and more layers. Eventually, the layers are lithified – turned to rock
The sediment (the sand, mud and pebbles) that make up Sedimentary rocks come from other rocks that have been worn down by wind, rain and snow.
Sedimentary rocks cover the majority of the Earth's rocky surface but only make up a small percentage of the Earth’s crust compared to metamorphic and igneous types of rocks.
breaks down rocks into small pieces known as sediment. This sediment is carried away by wind or water. The sediment eventually lands somewhere as sand or mud. Over time, new sediment piles on top of the old. The older layers become compressed and hard. In time, the sediment turns to rock. Sedimentary rocks only form about 8 percent of the rocks on Earth that cover the other types of rocks like a thin coat of paint. Even though they are only a tiny percentage of the rocks on Earth, they are very important. They tell us a lot about the history of life on earth because sedimentary rocks are the only type of rock that can hold fossils and they are formed in layers with the oldest rocks on the bottom and the newest rocks on the top.

17. Sedimentary Rock Clastic: Made of fragments of
previously existing rocks
Each layer is like the page of a book. One piece of paper is not heavy. But a stack of telephone books is very heavy and squishes anything underneath. Over time the layers of sand and mud at the bottom of lakes and oceans turns into rocks called sedimentary rocks. Over the course of millions of years, the igneous rocks are weathered down by forces of wind and water. Fine particles of dirt begin to cover the landscape. Often, these small rock particles end up being suspended in water, and find their way to the bottom of lakes, streams, and the ocean. Slowly, the layer of sediment on the bottom of lakes, and especially on the bottom of the ocean grows deeper and deeper, reaching depths of thousands of feet. The weight of all the sediment becomes immense, pushing down on lower layers of sediment with tremendous force. In addition, a number of minerals, which act like cement, bond the sediment together, causing it to form sedimentary rock.
Shale is clay that has been hardened and turned into rock. It often breaks apart in large flat sections.

18. Rounded pebbles cemented by
clay, mud, and sand
breccia
So how does rock become broken down in the first place to form the sediments that make up sedimentary rocks? Over time water, wind, heat, and ice wear the rock down causing it to fall apart. This process is called weathering and erosion. The weathered bits of rock are carried by what geologists call agents. Agents are streams, rivers, wind, glaciers, or really anything else that carries the bits of weathered rock away from the large rock that formed them. The most common agent is water in the form of streams or rivers. The weathered bits of rock are carried by the agent until the agent can't move them anymore. The weathered bits of rock pile up into a big pile. The weathered rocks are called sediments. The pile is called a sediment bed. Sediments are usually classified by size: Gravel is the biggest, sand is the next smallest, followed by mud, and silt is the smallest. Clastic sedimentary rocks are sedimentary rocks formed out of broken down bits of rocks. There are several kinds of clastic sedimentary rocks; they are categorized by the size and sometimes the shape of the pieces that make up the rock. Conglomerates are made from bits of rounded gravel that were deposited by the agent, usually water. Over time the wet pile of sediments becomes so heavy that the gravel gets compacted together, and minerals in the water cement the bits of gravel together. The only difference between conglomerates and breccias is: Conglomerates are made from rounded gravel and breccias are make from angular gravel. Arkose: 25% feldspar
23. conglomerate
25. arkose

19. Small sand-sized grains
Sandstone is basically the same. Piles of sand are piled up by water or wind and over time the piles get so heavy the sand is pressed together and cemented by minerals found in ground water. There are some interesting things that can be found in sandstone. Fossils are often found in sandstone. Also, have you ever been to the beach or a lake and looked out into the water and noticed that the sand is piled up in ripples by the motion of the waves? Sometimes the sand will get buried and the ripple pattern is preserved. Over time the sand will harden into rock and the ripple marks will still be in the rock
24. sandstone

20. Grains smaller than sand. Composed of
silt and clay-sized mineral particles that
we call “mud”
26. shale
Mudstone is the same as sandstone except the particles of rock that make up the mudstone are too small to be called sand. As the name sounds, the rock used to be mud that was buried and hardened into rock. Siltstone is made from even smaller particles than mudstone. Fossils can also be found in mudstone and siltstone. These types of rocks are sometimes called slate. Like “ripple marked” sandstone, mudstone can have marks made by water on it. Sometimes when mud hardens the surface cracks; these cracks can be preserved and harden into rock

21. Organic: made of organisms: directly or indirectly made
from material that was once living.

22. Made of shells of sea creatures
29. limestone
Limestone is often made from the fossilized remains of ocean life that died millions of years ago. The White Cliffs of Dover in England are made from the shells and remains of trillions of tiny animals that died more than 65 million years ago.
Chalk is a soft, white form of limestone
Biochemical sedimentary rocks are formed from the debris of life. For example, limestone is formed from out of decayed animal shells. Animals use calcium to form their shells. After the animal dies, the shell falls apart and the calcium combines with other elements and minerals and hardens into rock. Fossils are very common in this type of rock
chalk

23. Formed from the remains of plants
In swampy areas, plants die but they do not decay. Instead, they turn into peat. When the peat is compressed over millions of years, it becomes coal. Around 300 million years ago the world was covered with tropical swamp forest. When these plants died they fell into the swampy earth and over time were buried. Over millions of years they were changed into coal by pressure from the layers of rock above them.
coal
27. Oil Shale

24. chemical: formed when a lake dries up, leaving large
amounts of minerals that were dissolved in the water
Most of chemical sedimentary rocks come from minerals left behind by evaporated water! Halite is the mineral name for the substance that everyone knows as "salt." Its chemical name is sodium chloride, and a rock composed primarily of halite is known as "rock salt.”
Oil Shale: deposit of silt and organic debris on lakebeds and sea bottoms.
Mineral rich water drips into
the cave

25. 28.
Calcareous Tufa

26. Metamorphic Rocks
When rocks are buried deep within the Earth, tremendous heat,
great pressure, and chemical reactions may cause them to change
into different rocks with different textures and structures

27. layers or bands (foliated)
Metamorphic Rocks
When rocks are buried deep within the Earth, tremendous heat,
great pressure, and chemical reactions may cause them to change
into different rocks with different textures and structures
Mineral crystals are arranged
In parallel, thin, flat
layers or bands (foliated)

28. 16. slate
20. garnet schist
18.
gneiss

29. Metamorphic Rocks
When rocks are buried deep within the Earth, tremendous heat,
great pressure, and chemical reactions may cause them to change
into different rocks with different textures and structures
NOT arranged in layers and
do not break into layers
(unfoliated)

30. 21. marble
17. quartzite
22. Anthracite coal