Tomas Pueyo Profile picture
Apr 1 21 tweets 8 min read Read on X
This video of the Rock of Gibraltar gives an intuition for why some areas of the world have deserts next to rainforests

What's happening here?
How can you use that to predict where there will be deserts or rainforests?🧵
Look at the map below: In some places, deserts and lush forests are side by side. Why?

The mountain chains between them Image
The effect is called the Rain Shadow:
• Air comes wet from the sea
• As it hits mountains, it goes up
• Higher altitudes are cooler, so the air cools
• That condenses water (like the droplets on you Coke glass)
• Rain falls
• Air is dry past the mountains Image
That's what's happening in Gibraltar: You can see the water condense as the air lifts up

If the mountains are tall enough, they can completely stop the water
With this, you can predict where there are a bunch of rainforests and deserts in the world:
1. In what direction do winds blow?
2. Where are there tall mountain ranges?

The 1st question is mainly determined by the rotation of the Earth: Image
This is why around tropical areas, east coasts tend to be wet while everything west of a high mountain range tends to be dry:

Brazil and northern Argentina are wet, but past the Andes it's drier—like the Atacama Desert

Eastern Australia is wet, western Australia is drier.
Image
Image
This effect is inverted if you go further north or south
This inversion is most striking around the Andes Image
But the rotation of the Earth is not the only driver of winds. Monsoons are driven by big masses of land dragging in moist air from warm oceans. This is true in Africa, where monsoons come to central Africa from the west and southern Africa from the east
This creates 2 African deserts:

The Nile—which gives life to ~200M ppl—forms in the Ethiopian Highlands, which take all water from monsoon winds, leaving Somalia as a desert

The reverse is true southwards: eastern South Africa and Mozambique are wet, while Namibia is dry Image
The same is true in Asia. This is why India is so much wetter than Tibet. This is a side view of the Himalayas and Tibet.

Left: India (south)
Right: Tibet (north) Image
The same happens in in Northern Spain and Northwestern Africa: Prevalent winds come from the Atlantic, and both areas have mountains, catching the wind's moisture and creating vegetation

Past the mountains, it's dry or even desertic Image
Look at these 2 pictures. They're taken 5km away, before and after a tunnel in northern Spain
Image
Image
Similar effects can be seen in other areas of the world, where mountain ranges split deserts from rainforests. Here, in the Middle East, you have 3 such areas Image
This is how you get amazing pictures like those of Tehran, the capital of Iran, which is at the edge of a desert but towered by snowy mountains

If you thought Iran was just desert, I present you the Hyrcanian Rainforest

Image
Image
Image
This is also true in Saudi Arabia and Yemen. Why do you think people live mostly on the west and eastern borders (where Mecca and Medina are)? They get the little water carried by the wind from the Red Sea

Left: Arabian Peninsula
Right: Population density
Image
Image
This topographic map shows the mountains that cause all these rain shadows in Spain, northwestern Africa, Turkey, Iran, the Levant, and Saudi Arabia Image
So that's the rain shadow effect

I'm soon going to cover a very related (and hot) topic: Why are warmer countries poorer?
Follow me to see it, or better yet, subscribe to my free newsletter
unchartedterritories.tomaspueyo.com/subscribe
Sorry I meant west and southern borders
Somebody has mentioned the Foehn Wind, which is the dry wind that blows past the mountains. In the Bay Area it's part of @KarlTheFog
In the rest of the world, I think we call it rolling fog
What are other examples where this happens? Share pictures and maps!
Original Gibraltar video from @MetOGibraltar !

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More from @tomaspueyo

Jul 18
Here are the most FASCINATING facts I could find about Mexico:

1. Mexico is so huge it’s hard to comprehend. You can fit 30 European countries in Mexico and still have room to spare Image
Here's another way to look at it: Mexico vs Greenland
(from @neilrkaye)
2. As big as it's now, it used to be MUCH bigger
In the 1846-48 war with the US, the US took 55% of Mexico’s land! Image
Read 23 tweets
Jul 5
8% of Mexico hosts over 50% of its population
Why?
Understanding it also explains the Aztecs & their pyramids
🧵
This map shows crisply this area of high population density. Why there?
(cc @researchremora) Image
And it's not a very flat area. It's some of the most mountainous land in all of Mexico! Image
Read 26 tweets
Jun 30
Chile is so long, it's curved

How long is it?
Why not longer?
Why no other country is as long?
How does that make Chileans incomprehensible?

A thread about Chile and its humongous length
🧵
Chile is as long as the US and Canada combinedImage
Chile is as long as all of Europe!

It can stretch from Norway to Morocco
From London to Baghdad! Image
Read 24 tweets
Jun 10
What makes Budapest unique?
It wasn't just 2 cities (Buda + Pest) but 3-4!
Why?
And why is it where it is?
Why did it become the capital of Hungary?
It's no coincidence, and it explains the history of the country

Look at this:
Thread 🧵
The Pannonian Basin, this huge plain surrounded by mountains, was going to have a capital. But where would it be? Image
It would probably be on the main artery: the Danube, which splits the plain in half
1. Navigable all the way to Germany—fantastic for trade
2. Drinking water, great for living
3. Water for irrigation ➡️ crops

But early on the Danube had another huge advantage: Image
Read 22 tweets
Jun 6
Why is Hungary so small?
As this map shows, it could be bigger
It used to host one of the world’s most powerful empires—Austria-Hungary

Now it’s tinier & poorer. What happened?

Explaining it also explains Orbán, or why Hungarians hate their borders🧵 Image
You see that big plain surrounded by mountains? That's a perfect region for a single country: well-connected, fertile plains, protected by an easily-defensible wall of mountains.

That is, indeed, where Hungary was for nearly 1000 years!

It's called the Pannonian Basin
All these mountains catch humidity that flows down as rivers, which criss-cross the country, bringing lots of irrigation

The biggest one is the Danube, so big & gentle that it's navigable, connecting it with Germany & creating trade and wealth along its controllable path
Image
Image
Read 18 tweets
May 1
Two shocking events from last week unmasked eco-terrorists disguised as environmentalists:

1. The Philippines banned golden rice, condemning thousands of children to blindness and death
2. German Greens lied to closed nuclear plants

This is what happened and how to reverse it: Image
1. Golden Rice Ban
Golden Rice has added vitamin A over 100,000 children every year and turns blind over 100,000 more

Golden Rice has additional vitamin A, and eliminates that problem Image
But Greenpeace got a Filipino court to ban it. Why?
The court says "there's not enough evidence". But there is, proven by safety tests from countries like the US, Canada, and NZ. It is just like rice, except with more Vit A

So why do they say that?

reason.com/2024/04/25/gre…
Read 13 tweets

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