Hey there explorers, Bryan here with you for another expedition around the globe.
Have you ever wondered what cars are made of? Go on, take a guess.
Did you say metal? Well you're kind of right. More accurately, they're made up of lots of
metals and alloys: steel, aluminum, copper, lead, platinum, palladium, rhodium, magnesium,
titanium, the list is already long and we haven't even covered the non-metal materials in it like
glass, plastic, and rubber! The point is to make, take care of, or fix your car,
you need to know how it's built and the first step toward that is understanding what it's made of.
We've talked a lot about how to describe places using the themes of geography but we can't fully
understand places or the people living within them until we get to know the earth itself.
So today we'll begin a brief journey into the world of geology. Ready explorers?
If we want to study the earth we should know what it's made of and how it works. Before we
begin our study of the land and water, pause the video and show what you know in your lesson guide.
The people who study the earth's physical structure and history
are called geologists. We'll be taking a page out of their book as we learn about the land
and water. Our learning goals are to describe the earth's surface land and water composition,
to categorize things in the environment into different spheres,
and to identify ways that humans interact with those spheres.
If you were to fly up to space and view the earth from afar,
you'd quickly discover that it's a watery planet. More than 70% of the planet's surface is water,
mostly salt water in the form of oceans and seas. Do you know how many oceans the earth has?
Well some argue that 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
oceans. The large continuous expanses of land that rise above sea level separating those oceans are
called continents and there are seven of those: North America, South America, Europe, Africa,
Asia, Australia, and Antarctica. Sometimes an eighth continent, Oceania, is added to this list
to account for the islands scattered across the Pacific. Most of the time these islands are left
off the list because they don't really meet the description of continuous expanses of land. Asia
is the largest continent by far with 17.2 million square miles of land. Australia is the smallest
with just under 3 million square miles. Asia is also the largest continent in terms of population,
hosting more than 4.4 billion people. Over half the global population estimates suggest
that of every human to ever walk the earth, one out of 20 of them is living in Asia right now.
The least populated continent is antarctica which has research stations but no permanent residents.
Which continent are you most excited to learn about this year? Respond in your PDF.
Continents are made up of landforms, natural features of the surface of the earth.
A few examples include mountains, hills, plateaus, canyons, valleys, and plains. Landforms can also
include shoreline and submerged features such as bays, gulfs, peninsulas, seas,
mid-ocean ridges, and volcanoes. Can you identify some landforms that are near
your current location? Pause the video, look around outside, and see how many you can find.
Typically land forms are classified according to their relief, which is the difference in elevation
between their highest and lowest points. Mountains have high relief, hills which are
typically lower and rounder have lower relief. So what's the highest mountain in the world?
Everest, right? Well actually no, it's Mauna Kea in Hawaii.
Mount Everest stands at 29,031 feet above sea level, very impressive! Mauna Kea on the other
hand, stands at only 13,796 feet above sea level, and yet it's nearly a mile taller than Everest.
How is this possible? Well Mauna Kea extends 19,700 feet below the ocean surface,
over half of it is submerged in the waters of the Pacific so if we measure it by relief its total
height is a staggering 33,496 feet. Now don't worry Everest fans, Mount Everest is still the
tallest mountain on earth in terms of altitude, meaning the summit's elevation above sea level.
The earth's crust is composed of lots of different things classified into many spheres.
Soil, rocks, landforms, and other features of the earth's surface make up the lithosphere. The air,
water vapor, and other substances above the earth's surface make up the atmosphere. Water
on the surface, underground, and in the air makes up the hydrosphere. Sometimes the water
is permanently frozen and you'll hear that part of the sphere called the cryosphere.
And of course the biosphere is made up of the parts where life exists, it's the world of plants,
animals, and other living things on land and in the water. That's a lot of Greek vocabulary
so let's break down those words. Litho 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 and cryo means frozen so those are the spheres containing water and
ice. And finally because bio means life, the biosphere refers to where life is found.
We'll look at interactions among the spheres as well. For example, humans in the biosphere
might harness energy from the hydrosphere by having it spin turbines in the lithosphere
to produce electricity. Check out the practice questions in the lesson guide, they will help
you get more familiar with your vocab. Take a second to practice what you've learned.
As we continue our study of geography, we'll need to incorporate an understanding of the
earth when we think about the people who live in it. 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 what it's made of.
Challenge yourself to think about how land, air, and water shape the world around you.
And until next time, keep exploring!