---
title: "The Physical Map of the World"
book: "Primary & Middle School Earth and Space Sciences"
subject: earth
language: en
chapter: 9
exercises: 11
source: https://one-course.com/books/earth/1/en/chapter/9-the-physical-map-of-the-world
license: CC-BY-NC-SA-4.0
credit: "One Earth and Space Sciences Book, One Course (one-course.com)"
---

# Chapter 9 — The Physical Map of the World

Sami and Noor unfold a big [map](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#def-g2-drawing-to-map-map) of the world on the classroom floor and kneel around it. It is not like the [maps](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#def-g2-drawing-to-map-map) they know. There are no countries, no borders and no towns. Instead, the land is painted in colours: green along the [coasts](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) and in the great flat lands, then pale yellow, then brown, and in a few places almost white. The [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean), too, has several blues: pale near the [coasts](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water), darker and darker far out in the [oceans](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean).

“Why is that part of Asia white?” asks Noor. “Is it [snow](https://one-course.com/books/earth/1/en/chapter/7-clouds-rain-and-snow#def-g4-clouds-rain-snow-precipitation)?” Not quite. On this [map](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#def-g2-drawing-to-map-map), every colour tells how high the land is, or how deep the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean).

**You already know.**

A [map](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#def-g2-drawing-to-map-map) shows a place from above, made smaller; its [legend](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#def-g2-drawing-to-map-legend) explains its colours and symbols ([Chapter 4](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#ch-g2-drawing-to-map)). The land is gathered in seven [continents](https://one-course.com/books/earth/1/en/chapter/6-the-globe-continents-and-oceans#def-g3-continents-and-oceans-continent), between five [oceans](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean), and a [world map](https://one-course.com/books/earth/1/en/chapter/6-the-globe-continents-and-oceans#def-g3-continents-and-oceans-world-map) is a flattened [globe](https://one-course.com/books/earth/1/en/chapter/6-the-globe-continents-and-oceans#def-g3-continents-and-oceans-globe) ([Chapter 6](https://one-course.com/books/earth/1/en/chapter/6-the-globe-continents-and-oceans#ch-g3-continents-and-oceans)). [Mountains](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform), [hills](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform), [valleys](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform) and [plains](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform) are the [landforms](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform); [rivers](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) flow from high land down to the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) ([Chapter 2](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#ch-g1-landscapes-around-us)).

## 9.1 Reading a physical map

To say how high a place is, we need a starting level, the same everywhere on Earth. We take the level of the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean).

**Definition 9.1 (Altitude and sea level).**

*Sea level* is the average level of the surface of the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean), between high and low tide. The *altitude* of a place is its height above [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) level, in metres. Under the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean), we speak of *depth*: how far the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) floor lies below [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) level.

A town by the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) has an [altitude](#def-g4-world-physical-map-altitude) of a few metres. A village in the [mountains](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform) may stand at 1 500 metres: one and a half kilometres above the level of the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean), even if it is hundreds of kilometres from any [coast](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water).

**Definition 9.2 (Relief).**

The *relief* of a region is the shape of its land: where it is high and where it is low, its [mountains](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform), plateaus, [valleys](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform) and [plains](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform).

**Definition 9.3 (Physical map).**

A *physical map* shows the [relief](#def-g4-world-physical-map-relief) of the land and the depth of the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) with colours, one colour for each step of [altitude](#def-g4-world-physical-map-altitude) or depth, and the great [rivers](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water), [lakes](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water), deserts and ice.

![The physical map of the world, with its legend. Each colour is one step of altitude (on land) or of depth (under the sea). Rivers in dark blue. The relief is drawn from one value every degree of latitude and longitude (about every 100 kilometres), so it is smoothed: single summits and narrow trenches do not show. Data: NOAA ETOPO1 relief; rivers, lakes and coastlines from Natural Earth.](https://one-course.com/images/onecourse/chapters/earth-1/g4-world-physical-map/fig-6cf58514bce2.svg)

![The physical map of the world, with its legend. Each colour is one step of altitude (on land) or of depth (under the sea). Rivers in dark blue. The relief is drawn from one value every degree of latitude and longitude (about every 100 kilometres), so it is smoothed: single summits and narrow trenches do not show. Data: NOAA ETOPO1 relief; rivers, lakes and coastlines from Natural Earth.](https://one-course.com/images/onecourse/chapters/earth-1/g4-world-physical-map/fig-966a74e6b65e.svg)

*The [physical map](#def-g4-world-physical-map-physical-map) of the world, with its [legend](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#def-g2-drawing-to-map-legend). Each colour is one step of [altitude](#def-g4-world-physical-map-altitude) (on land) or of depth (under the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean)). [Rivers](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) in dark blue. The [relief](#def-g4-world-physical-map-relief) is drawn from one value every degree of latitude and longitude (about every 100 kilometres), so it is smoothed: single summits and narrow trenches do not show. Data: NOAA ETOPO1 relief; [rivers](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water), [lakes](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) and coastlines from Natural Earth.*

**Method 9.4 (Reading a colour on a physical map).**

To find the [altitude](#def-g4-world-physical-map-altitude) of a place on a [physical map](#def-g4-world-physical-map-physical-map):

1. find the place, and look at its colour;
2. find the same colour in the [legend](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#def-g2-drawing-to-map-legend) ;
3. read the step under it: the [altitude](#def-g4-world-physical-map-altitude) of the place lies between the two numbers.

The same works at [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean), for the depth.

**Example 9.5 (Three places).**

The mouth of the Amazon, on the [coast](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) of South America, is dark green: its [altitude](#def-g4-world-physical-map-altitude) is between 0 and 200 metres. The middle of the Sahara is pale green or pale yellow: between 200 and 1 000 metres. The plateau north of the Himalaya, in Asia, is almost white: above 4 000 metres.

## 9.2 The great mountain ranges

On the [map](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#def-g2-drawing-to-map-map), the brown and white colours are not spread evenly. They form long, narrow bands.

**Definition 9.6 (Mountain range).**

A *mountain range* is a long line of [mountains](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform), joined together, that stretches over hundreds or thousands of kilometres.

The Andes run along the whole west side of South America. North America has the Rocky [Mountains](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform), Europe the Alps, and Asia the highest of all: the Himalaya. There stands the highest [mountain](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform) on Earth: Mount Everest, 8 849 metres high, measured again in 2020.

![The Himalaya seen from the International Space Station, looking south from the high plateau of Tibet: a sea of snow-covered summits. Photograph: NASA (public domain).](https://one-course.com/images/onecourse/chapters/earth-1/g4-world-physical-map/img-b6afc5325a3d.jpg)

*The Himalaya seen from the International Space Station, looking south from the high plateau of Tibet: a sea of snow-covered summits. Photograph: NASA (public domain).*

## 9.3 The great rivers and lakes

[Rain](https://one-course.com/books/earth/1/en/chapter/7-clouds-rain-and-snow#def-g4-clouds-rain-snow-precipitation) and melted [snow](https://one-course.com/books/earth/1/en/chapter/7-clouds-rain-and-snow#def-g4-clouds-rain-snow-precipitation) run off the land, join into streams and then into [rivers](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water), and the [rivers](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) carry the water down to the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean). The largest [rivers](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) drain whole regions of a [continent](https://one-course.com/books/earth/1/en/chapter/6-the-globe-continents-and-oceans#def-g3-continents-and-oceans-continent).

The two longest [rivers](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) on Earth are the Nile, in Africa, and the Amazon, in South America. Each is close to 7 000 kilometres long. Which one is the longest? Nobody agrees for sure, because it depends on where you decide that a [river](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) starts: among all the little streams that join to make it, which one counts as its true beginning? In 2007, a team that followed the Amazon to a farther source said it was about 6 800 kilometres long, a little longer than the Nile; many reference books still call the Nile the longest.

The Amazon is, without any doubt, the largest [river](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water): it carries more water than any other.

![The Amazon, brown with mud, winding through the rainforest, seen from the International Space Station. Photograph: NASA (public domain).](https://one-course.com/images/onecourse/chapters/earth-1/g4-world-physical-map/img-d11ad735d6c8.jpg)

*The Amazon, brown with [mud](https://one-course.com/books/earth/1/en/chapter/5-stones-pebbles-and-sand#def-g3-stones-pebbles-sand-sand), winding through the rainforest, seen from the International Space Station. Photograph: NASA (public domain).*

[Lakes](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) also break records. The largest [lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) on Earth is the Caspian Sea, between Europe and Asia: it is so big that it is called a [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean), but it is closed in by land on every side. It covers more than 370 000 square kilometres. The deepest [lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) is [Lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) Baikal, in Russia: in places its bottom lies nearly 2 kilometres below its surface.

## 9.4 Deserts and the great ice

Two kinds of places stand out on the [physical map](#def-g4-world-physical-map-physical-map) because almost nothing grows there: the great deserts, where it almost never [rains](https://one-course.com/books/earth/1/en/chapter/7-clouds-rain-and-snow#def-g4-clouds-rain-snow-precipitation), and the great ice.

The Sahara, in the north of Africa, is the largest hot desert on Earth. It covers about eight and a half million square kilometres. Africa as a whole covers about 30 million square kilometres, so the Sahara is a little more than a quarter of the [continent](https://one-course.com/books/earth/1/en/chapter/6-the-globe-continents-and-oceans#def-g3-continents-and-oceans-continent): more than $\frac{1}{4}$, but less than $\frac{1}{3}$.

The great ice covers Antarctica, around the [South Pole](https://one-course.com/books/earth/1/en/chapter/6-the-globe-continents-and-oceans#def-g3-continents-and-oceans-poles), and most of Greenland, in the far north of the Atlantic. There, the [snow](https://one-course.com/books/earth/1/en/chapter/7-clouds-rain-and-snow#def-g4-clouds-rain-snow-precipitation) of thousands of years has piled up and turned into a thick layer of ice. On the [physical map](#def-g4-world-physical-map-physical-map), their colours are those of high land, because the top of the ice is high above [sea level](#def-g4-world-physical-map-altitude).

## 9.5 The highest and the deepest

The [physical map](#def-g4-world-physical-map-physical-map) shows the shape of the Earth’s surface, but it is so small that it hides the extremes. Let us put them side by side, to scale.

![From the deepest point of the ocean to the highest summit, to scale. The Challenger Deep, in the Pacific Ocean, lies deeper below the sea than Mount Everest rises above it. Values: Everest 8 849 m; the Challenger Deep nearly 11 000 m; the average ocean floor about 3 700 m.](https://one-course.com/images/onecourse/chapters/earth-1/g4-world-physical-map/fig-121c63378108.svg)

*From the deepest point of the [ocean](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) to the highest summit, to scale. The Challenger Deep, in the Pacific [Ocean](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean), lies deeper below the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) than Mount Everest rises above it. Values: Everest 8 849 m; the Challenger Deep nearly 11 000 m; the average [ocean](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) floor about 3 700 m.*

**Example 9.7 (Everest in the deep).**

If we could lift Mount Everest and set it down at the bottom of the Challenger Deep, its summit would still be under the water: about 11 000 metres of trench, against 8 849 metres of [mountain](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform). More than 2 kilometres of [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) would still cover it.

## 9.6 Exercises

**Exercise 9.1 ★.**

What is the [altitude](#def-g4-world-physical-map-altitude) of a place? From which level is it measured?

**Solution of Exercise 9.1.**

The [altitude](#def-g4-world-physical-map-altitude) of a place is its height above [sea level](#def-g4-world-physical-map-altitude), in metres. It is measured from [sea level](#def-g4-world-physical-map-altitude), the average level of the surface of the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean).

**Exercise 9.2 ★.**

Using the [legend](https://one-course.com/books/earth/1/en/chapter/4-from-a-drawing-to-a-map#def-g2-drawing-to-map-legend) of the [physical map](#def-g4-world-physical-map-physical-map), give the [altitude](#def-g4-world-physical-map-altitude) of a place coloured: (a) dark green; (b) pale yellow; (c) almost white.

**Solution of Exercise 9.2.**

(a) Dark green: between 0 and 200 metres. (b) Pale yellow: between 500 and 1 000 metres. (c) Almost white: above 4 000 metres.

**Exercise 9.3 ★.**

On which [continent](https://one-course.com/books/earth/1/en/chapter/6-the-globe-continents-and-oceans#def-g3-continents-and-oceans-continent) is: (a) the Andes; (b) the Himalaya; (c) the Sahara; (d) the Rocky [Mountains](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform)?

**Solution of Exercise 9.3.**

(a) South America. (b) Asia. (c) Africa. (d) North America.

**Exercise 9.4 ★.**

Name the highest [mountain](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform) on Earth, the largest [lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) and the deepest [lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water).

**Solution of Exercise 9.4.**

The highest [mountain](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform) is Mount Everest (8 849 metres). The largest [lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) is the Caspian Sea; the deepest [lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) is [Lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) Baikal.

**Exercise 9.5 ★.**

On the [physical map](#def-g4-world-physical-map-physical-map), the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) near the [coasts](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) is pale blue and the middle of the [oceans](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) dark blue. What does that tell you about the depth of the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean)?

**Solution of Exercise 9.5.**

The darker the blue, the deeper the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean): the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) is shallow near the [coasts](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) (less than 200 metres) and much deeper in the middle of the [oceans](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) (more than 4 000 metres in many places).

**Exercise 9.6 ★.**

Why are Antarctica and Greenland coloured like high land on the [physical map](#def-g4-world-physical-map-physical-map)?

**Solution of Exercise 9.6.**

The [physical map](#def-g4-world-physical-map-physical-map) shows the [altitude](#def-g4-world-physical-map-altitude) of the surface. In Antarctica and Greenland the surface is the top of a thick layer of ice, which lies high above [sea level](#def-g4-world-physical-map-altitude), so they get the colours of high land.

**Exercise 9.7 ★★.**

Put in order, from the lowest to the highest: a beach; a village at 1 500 metres; the top of Mount Everest; the bottom of the Challenger Deep; the average floor of the [ocean](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean).

**Solution of Exercise 9.7.**

The bottom of the Challenger Deep (nearly 11 000 metres below [sea level](#def-g4-world-physical-map-altitude)); the average floor of the [ocean](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean) (about 3 700 metres below); a beach (about 0 metres); a village at 1 500 metres; the top of Mount Everest (8 849 metres).

**Exercise 9.8 ★★.**

Why can’t we say for sure whether the Nile or the Amazon is the longest [river](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water)?

**Solution of Exercise 9.8.**

A [river](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) is made of many streams that join together, and people do not agree on which stream is its true beginning. Measured from a farther source, a [river](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) is longer. The Nile and the Amazon are so close in length (each about 6 700 to 6 800 kilometres) that the answer depends on that choice.

**Exercise 9.9 ★★.**

Africa covers about 30 million square kilometres. Which part of it is a quarter? A third? The Sahara covers about eight and a half million square kilometres: is it more or less than a quarter of Africa? More or less than a third?

**Solution of Exercise 9.9.**

A quarter of 30 million is seven and a half million square kilometres (30 divided by 4); a third is 10 million (30 divided by 3). The Sahara, eight and a half million, is more than a quarter of Africa but less than a third.

**Exercise 9.10 ★★.**

A [mountain](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-landform) hut stands at 2 500 metres, and a [lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water) below it at 1 000 metres. How many metres higher is the hut? Which colours do they have on the [physical map](#def-g4-world-physical-map-physical-map)?

**Solution of Exercise 9.10.**

$2500 - 1000 = 1500$: the hut is 1 500 metres higher. The hut, between 2 000 and 4 000 metres, is brown; the [lake](https://one-course.com/books/earth/1/en/chapter/2-landscapes-around-us#def-g1-landscapes-around-us-water), at 1 000 metres, is at the boundary between pale yellow (500 to 1 000) and light brown (1 000 to 2 000): either is accepted.

**Exercise 9.11 ★★★.**

A plane flies 10 kilometres above [sea level](#def-g4-world-physical-map-altitude). Is it higher than Mount Everest? By how many metres? If it flew over the Challenger Deep, how far above the bottom of the trench would it be (take 11 000 metres for the trench)?

**Solution of Exercise 9.11.**

10 kilometres is 10 000 metres. $10000 - 8849 = 1151$: the plane is higher than Mount Everest, by 1 151 metres. Over the Challenger Deep, it is 10 000 metres above the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean), and the bottom of the trench is 11 000 metres below the [sea](https://one-course.com/books/earth/1/en/chapter/3-water-on-earth#def-g2-water-on-earth-ocean): $10000 + 11000 = 21000$ metres above the bottom of the trench.