What is Soil? Video Lecture | Science Olympiad Class 7

unless you spent a lot of time
underground like we do you might not
think very often about dirt but dirt is
awesome
it's everywhere and just about every
living thing on earth depends on it from
the plants that grow in it to the
animals that eat the plants to the
animals that eat those animals that's
why we're really glad that one of our
viewers four year old Caleb from
Mississippi wrote to ask us what is dirt
great question first of all the stuff
that fills our flowerpots and baseball
fields may just be dirt to us but
scientists have a different name for it
they call the top layer that covers most
of the land soil so what is soil well
it's a mixture of things how soil looks
and feels depends on where you are so
some very dry places have a lot of
gritty sand in the soil while soil in
other parts of the world might have hard
rocks soft clay or even pieces of
seashell in it usually those soil is
made of four main things mostly soil is
made up of minerals minerals are hard
stony substances that form things like
rocks sand and clay the next big part of
soil is water that's right even if a
clump of dirt doesn't seem like mud to
you it actually has water in it all
living things need water to survive and
soil does a great job of holding on to
water for plants animals and other
things that live in it and you know what
else is in the soil that you probably
can't tell us they're air just like
water air in the soil is important
because living things need air - it
feels the spaces between all those
little bits of minerals water and other
parts of the soil and the beauty of it
is the animals that live in the soil
actually help more water and air get
inside it creatures like worms and
insects and even small mammals like
moles and mice dig tunnels down in the
dirt those tunnels let air and water
trickling and flow around so that even
deep down the soil has what living
things need to make a nice home there
and this my friends brings us to
probably the most important part of soil
in fact it's some of the most important
stuff on earth scientists call it
organic matter organic matter includes
anything that's alive like those worms
and insects but also parts of plants and
even living things that we can't even
see like bacteria plus organic matter
also includes
things that used to be alive like dead
plants and animals after those things
died other living things like fungi
bacteria insects and worms eat what's
left of those plants and animals and
break them down into very small pieces
this broken down material puts nutrients
back into the soil and plants then use
those nutrients to grow so soil is where
plants get their food scientists call
this special nutrient-rich part of the
soil by its own name houmous houmous is
what gives oil its dark brown color and
it even sometimes contains special
bacteria that makes soil smell well
dirty now all of these things are mixed
together to make soil but the mixture
isn't always the same scientists have
found that soil has many layers to it
the top layer is all made up of organic
matter with lots of that good useful
houmous beneath that is the layer that
we often call topsoil topsoil is made
mostly of houmous with a little bit of
minerals sprinkled in this layer is
where seeds start to grow as you go
further down away from the surface you
find that the deeper layers of soil
contain more minerals than humans and
once you get through the bottom layer
you run into a layer of solid rock so
now you have the dirt on soil and you
know it's made of a minerals water air
and organic matter thank you for asking
Caleb does anybody else have a question
let us know by either leaving a comment
or emailing us at kids at the scishow
com
thanks guys and see you next time on
scishow kids
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