Download Geology The difference between rocks and minerals

Geology
The difference between rocks and minerals:
It’s not easy to tell the difference between rocks and minerals because there are so many
kinds of them. It takes years of study to be able to accurately identify a mystery rock.
Rocks are made of 2 or more minerals, but minerals are not made of rocks.
What are the different types of rocks?
Igneous rocks are formed when melted rock cools and solidifies. Melted rock may come
in the form of magma, when it is found underneath the Earth’s surface. It can also come
in the form of lava, when it is released onto the Earth’s surface during a volcanic
eruption.
Some examples of igneous rocks are granite, scoria, pumice, and obsidian.
Pumice, for instance, is formed when lava made up of melted rock, water, and trapped
gas is ejected from a volcano during a violent eruption. As the ejected material undergoes
very rapid cooling and depressurization, some of the trapped gas escape, leaving holes
and gas bubbles on the solidified material.
Sedimentary rocks start forming when soil and other materials on the Earth’s surface are
eroded and finally settle down, forming one layer of sediments. As time passes, more and
more materials get eroded and settle on the older layers. Thus, layer upon layer is formed.
The lower layers undergo intense pressure due to the weight of the upper layers,
eventually evolving into rocks.
Some examples of sedimentary rocks are sandstone, limestone, shale, conglomerate, and
gypsum.
Sandstone, for instance, is a result of depositions of sand from beaches and rivers. You
can find them mostly in deltas, since this is where the rivers flow into the ocean.
Metamorphic rocks are actually products of rocks that have undergone changes. A
metamorphic rock may have originally been an igneous, sedimentary, or even another
metamorphic rock.
The changes occur when the original rocks are subjected to extreme heat and pressure
beneath the Earth’s surface.
Some examples of metamorphic rocks are marble, slate, schist and gneiss.
Marble, for instance is the result of the metamorphism of limestone and dolostone. When
limestone metamorphoses, its calcite grains grow and interlock with one another. As
such, marble is denser and harder compared to limestone.
The Fizz Test
Many rocks can look alike. Sometimes telling the difference between a limestone or
marble and other rocks such as shale and quartzite can be difficult. One way that
geologists test the rocks is by performing the acid or “Fizz” test.
1. Gather the samples you want to test. Some good choices are limestone, oolitic
limestone, coquina and marble. You should see some “fizzing” with these
samples.
2. Drop, using a straw or dropper, or pour your acid (lemon juice contains citric
acid) on one rock sample at a time.
3. Look through your hand magnifier right away to see the bubbles. The bubbles will
be small so look closely.
4. Do you see the bubbles? If so, what do they look like? The fizz is telling you that
your rock is a limestone or contains calcite like limestone (coquina).
5. Use other samples such as shale, slate, and quartzite to observe samples, which
should not “fizz.” Mix up your samples and see if you can figure out what they
are using the fizz test!
How do Volcanoes work?
Volcanoes form when chambers of magma, or hot molten rock, boil to the surface. These
magma chambers often remain sealed for hundreds of years between eruptions, until the
pressure builds sufficiently to break through a vent, which is a crack or weak spot in the
rock above.
The blast creates a crater, where lava and ash spill out, forming the cone. On some
volcanoes, the magma chamber collapses after a violent eruption and a caldera forms,
which is just a large, bowl-shaped crater.
Where do volcanoes form?
Earth's crust is made up of a dozen or so major plates, each moving about four inches a
year. Rising magma pushes Earth's plates apart in the middle of the oceans. Here and
along other weak spots in the plates, hot spots occur.
The Hawaiian Islands were created by a hot spot. When an oceanic plate slides under a
continental plate, it creates a subduction zone. The rock is heated again as it dives into the
Earth, and magma again rises to form volcanoes.
Volcano Eruption
A volcano is produced over thousands of years as heat and pressure build up. That aspect
of a volcano is very difficult to recreate in a home experiment. However this volcano will
give you an idea of what it might look like when a volcano erupts flowing lava. This is a
classic experiment in which a chemical reaction can create the appearance of a physical
volcano eruption. You should look at pictures of volcanoes to be familiar with the
different types. (A shield volcano, for example is the most common kind of volcano, and
yet few people know about them) The reaction will bubble up and flow down the side
like a real volcano (only much faster!)
1. First make the 'cone' of the baking soda volcano. Mix 6 cups flour, 2 cups salt, 4
tablespoons cooking oil, and 2 cups of water. The resulting mixture should be
smooth and firm (more water may be added if needed).
2. Stand a soda bottle in the baking pan and mold the dough around it into a volcano
shape. Don't cover the hole or drop dough into it.
3. Fill the bottle most of the way full with warm water and a bit of red food color
(can be done before sculpting if you don't take so long that the water gets cold).
4. Add 6 drops of detergent to the bottle contents. The detergent helps trap the
bubbles produced by the reaction so you get better lava.
5. Add 2 tablespoons baking soda to the liquid.
6. Slowly pour vinegar into the bottle.