hey everyone it's nicholas so far we've explored the geographic themes of location
character place region movement and interaction and we've considered how
geographers use these themes to make sense of places on earth and the people who live in them
but we can't fully understand places or people or how people live in places unless we understand
some basics about the earth itself join me as we take a brief journey into the world of geology
ever wonder what cars are made of go on take a guess if you said metal you're mostly right more
accurately they're made from lots of different metals steel aluminum copper lead platinum
palladium rhodium magnesium titanium the list is long there's also lots of glass plastic and rubber
in most modern cars the point is to make fix study or take care of a car you need to know how it's
built and the first thing you need to know about how it's built is that's right what it's made of
likewise if you want to study the earth you need to know how it's built and what it's made of the
people who study earth's physical structure and history are called geologists geology is
a relatively new science but it deals with very ancient history in fact it deals with the most
ancient history of all the history of the earth itself which goes back about 4.6 billion years as
you can imagine the earth has seen a fair bit of change over those 4.6 billion years and geologists
in addition to trying to understand how the earth is put together work to identify those changes
explain causes and effects and predict how the earth might change in the future so what is earth
made of if you were to examine a photograph of earth taken from space you'd come to the
conclusion very quickly that it's a watery planet more than 70 water in fact most of it salt water
in the form of oceans and seas do you know how many oceans the earth has well some argue there's
only one an interconnected global ocean but most countries recognize five named oceans the pacific
the atlantic the indian the arctic and the southern the large land masses in the oceans are
called the continents and there are seven north america south america europe africa asia australia
and antarctica an eighth continent oceania is sometimes added to that list asia is the
largest continent at 17.21 million square miles and australia is the smallest at 2.97 million
square miles asia is also the largest continent in terms of population at over 4.4 billion people
the least populated is antarctica which has research stations but no permanent residence and
yet has somehow been the birthplace of at least 11 children since 1978. also antarctica has no
time zones contains 90 of the world's ice holds 70 of the world's fresh water in the form of glaciers
and has a number of ice-free valleys that haven't received rain in 2 million years continents
are made up mostly of landforms a landform is a natural feature of the surface of the earth a few
examples mountains hills plateaus canyons valleys and plains landforms can also include shoreline
features and submerged features such as bays peninsulas seas mid-ocean ridges volcanoes and
ocean basins typically landforms are classified according to differences in relief which is the
difference in elevation between the highest and lowest points mountains have high relief
hills which are typically lower and rounder have lower relief so wait what's the actual difference
between a mountain and a hill the elevation of the surrounding land determines that for example
a mountain in ireland which sits at a relatively low elevation might be considered a hill in the
rockies which sit at a relatively high elevation so what's the highest mountain in the world
everest right well no it's mauna kea in hawaii mount everest stands at 29 029 feet above sea
level very impressive mauna kea on the other hand stands only 13 796 feet above sea level
and yet it's nearly a mile taller than everest how is this possible because mauna kea extends 19 700
feet below the ocean which puts mauna kea at a total height of 33 496 feet well okay at least
the highest point on earth as measured from the center of the earth is mount everest right well
no the highest point on earth is mount chimorazo in ecuador wait what everyone knows mount everest
is the highest point on earth right well as we learned before the belief that earth is
round rather than flat originated with the ancient greeks and the notion that the earth is a perfect
sphere grew from that early hypothesis but guess what the earth is not a perfect sphere wait what
the earth isn't a perfect sphere no it's not it's an oblate spheroid which means it bulges at the
equator and flattens at the poles as a result of its rotation mount everest as we know stands
twenty nine thousand twenty nine feet above sea level mount chimborazo stands at twenty thousand
five hundred and forty nine feet nearly eight thousand five hundred feet lower but because
mount chimborazo is located just one degree 28 minutes south of the equator earth's fattest point
it gets a boost of some 13 miles further from the center of the earth which puts its height at 3967
miles from the center of the earth two miles more than the distance from the center of the earth to
the summit of mount everest don't worry mount everest fans everest is still the highest point
on earth in terms of altitude meaning it summits elevation above sea level geologists will tell
you that the earth has essentially three layers the core made of hot iron and nickel the mantle
a thick layer of rock and the crust earth's thin rocky surface and we'll get into that later but
for this lesson it's important to understand that the different elements of the earth's
natural environment are often thought of as a set of related spheres dominated by particular
physical forms what does that mean well soil rocks landforms and other features on the earth's
surface make up the lithosphere the layer of air water and other substances above the surface
make up the atmosphere water on the surface underground and in the air make up the hydrosphere
the biosphere is made up of the parts of earth where life exists the world of plants animals
and other living things that live in the land and water hold on that's a lot of greek vocabulary
let's take a quick look at these words litho in greek means stone the lithosphere is therefore
the sphere where the rocks are atmos means vapor so the atmosphere is the sphere where the air is
hydro means water the hydrosphere is where the water is and finally because bio means life
the biosphere is where life is found if you can remember what those prefixes mean you can remember
what each sphere contains geologists study interactions among the spheres for example humans
in the biosphere might harness energy from the hydrosphere by having water spin turbines in the
lithosphere to produce electricity we'll continue to talk about spheres but for now we're going to
place them in our toolkit of geographic concepts and vocabulary for future reference as we move on
in our study of geography i want you to include the science of geology in the way you think about
the earth in the same way an auto mechanic thinks about cars and how they're put together i want you
to think about the earth and how it's put together challenge yourself to think about how land air and
water might shape the world around you soon we'll be talking about some of the most powerful forces
within the earth and how they change the landscape and how people adapt until then keep exploring