on april 30th 2014 astronauts aboard the
international space station finish
installing high definition cameras
pointing down at planet earth
the project's known as a high definition
earth viewing experiment and shortly
after becoming operational nasa began
streaming in real time
these pictures down earth through the
internet for anyone to see
these are some of the most amazing
videos that i've ever seen of the planet
and it's kind of crazy to think that
everything we care about for the entire
human race depends on this relatively
small blue planet
the earth is our home and all the things
we care about like our families our
culture our history our technology our
knowledge they're all intimately related
to the history of this planet
but how exactly do we study the earth
the branch of science dedicated to
understanding the planet is called
geology and it's the study of the
earth's physical structure its history
and the processes that act on it
geologists are scientists that are
trying to learn about the history of the
earth through studying the rocks that
make it up
and understand the changes that the
planet is undergoing
since the surface of the earth is
constantly changing through time
learning about how rocks change can
allow scientists to better understand
our home
so let's start with the basics
every rock on the planet will fall into
one of three categories that is
sedimentary metamorphic and igneous
and it's these three rock types that
make up something called the rock cycle
that's just a process that by which new
rocks are formed and all rocks are
broken down on earth
but for this video i'm only going to
focus on igneous rocks because we can
actually watch their formation in real
time and understanding their formation
will give us a good foundation in
geology
the word igneous is derived from the
latin word ignis meaning fire that's
because igneous rocks begin their lives
as molten rock or lava below the surface
and given enough time that lava can be
brought to the surface of the earth by
way of volcanoes like these ones
now keep in mind that isn't the only way
igneous rocks can form but it is easiest
for us to see and conceptualize
there are over 1500 active volcanoes on
the earth today and many more ancient
inactive
volcanoes
igneous rocks are constantly being
recycled and formed in the rock cycle
and this has been going on since the
beginning of earth's history
we kind of think the planet as a static
place in terms of a human life it
appears that way to us but actually the
earth is really dynamic and by observing
igneous rocks we can see
how dynamic the planet is
so it seems pretty straightforward how
rocks form
molten lava comes out of the volcano
cools to form new rocks
but there's actually a lot more going on
below the surface than we realize
the earth is divided up in three major
parts
that is a crust where we live
and build our homes for example
the mantle
well rocks get heated and pressurized
and turned into something a little bit
more like silly putty a plastic
and the core
and it's these three parts that interact
that cause the earth to have a rock
cycle
it's because of this rock cycle
that rocks aren't used up
they're recycled through the planet
and geology
is trying to understand
all these processes that are controlling
the rock cycle
the earth
the changes that's undergone
its history
the rock cycle exists because the earth
has three dynamic parts the crust the
mantle and the core you can see them
here in this diagram
and because of the interaction of these
three parts igneous rocks can be formed
volcanic eruptions
one place to see this happen in real
time is on the big island of hawaii
this lava flowing out of a volcano cools
to form brand new igneous rocks
thickness rocks in this picture are
called basalt and that's because they're
rich in elements like magnesium and iron
it gives them that dark color
basalt's a really common kind of rock
you can find it all over the world just
like these stones in the rock wall
behind me they're the same kind of rock
as the lava flow we saw in hawaii
but there's no active volcanoes in
arizona so how did they get here
well these pieces of basalt are millions
of years old they came out of an ancient
volcano an eruption just like what we
saw in hawaii and one thing we can begin
to understand when we learn about
geology is that the earth is really old
and it's kind of amazing to think that
these rocks have survived for millions
of years
and the rocks that were farming new in
hawaii will be around for millions of
years
it's all about the rock cycle
so i'm standing here on a large piece of
granite in the santa catalina mountains
in southern arizona
and granite is a different kind of
igneous rock than basalt granite takes a
long time to cool and so the crystals
are larger unlike basalt like the lava
we saw in hawaii which cooled rapidly
the crystals are very fine and small and
you can't see them very well with your
eye granite on the other hand takes a
long time to cool and so the crystals
become much larger
that's the textural difference between
this rock and the basalt
being curious about the world around us
is the heart of geology it's about
understanding the planet that we live on
and what makes it up
in this video we learned the basics of
geology the three rock types in the rock
cycle
how igneous rocks are formed
the three parts of the earth
some of the differences between two
types of igneous rocks basalt and
granite
in the next video we'll learn about
sedimentary rocks if you have any
questions about igneous rocks feel free
to ask them in the comments below
thanks for watching and stay curious
about the natural world