For Kids · The land and the sky · The ground under you

The ground under Reykjavík

Capital Region · Nordic & Baltic Boreal · basalt country

Fall · October 6, 2026

Reykjavík, Capital Region

Nordic & Baltic Boreal·Hardiness zone 7b

Try it

Dig down under Reykjavík

Drag the spade down, or tap Dig deeper, through the leaves, the living topsoil and the subsoil, all the way to the bedrock that is really down there.

About 0 cm down

The grass

the top of the ground

Under the grass is a whole hidden world. Drag the spade down — or press Dig deeper — to find out what is down there.

Layer 0 of 5

It takes hundreds of years to make one centimetre of topsoil. The depths are typical — every place is different — and the ruler is squashed at the bottom so the rock fits on the screen.

Say it like this

Age 2“Dig, dig, dig! Who lives down there? A wiggly worm!”
Age 4“Leaves, dark soil, lighter soil, broken rock, solid rock. Can you count the layers? Five!”
Age 6“Topsoil is made of rotted leaves and tiny bits of broken rock. Why do you think it takes hundreds of years to make?”

Go outside: Dig a small hole in the garden and count how many worms live in one shovelful — then put them all back and fill it in.

The river right now

Water near Reykjavík is running high

146%

of the ten-year median for this date · 6.3 m³/s against 4.3 normally

high

drynormal for the dateflood

Running high for the date. Water will be pushy and coloured, fish will be tucked into the slack water at the edges and behind obstructions, and crossings that are normally easy are not. It is dropping, roughly 17% over the week ahead.

Under your feet

Reykjavík sits on basalt

About 66 million years old — after the dinosaurs, as mammals and grasslands spread.

All the kinds of rock, and how each one forms →

At the surface66 million years oldNeither way
Basalt
Tertiary-Quaternary volcanic: mafic rocks · Tertiary
What it is
The commonest rock on Earth's surface, and the floor of every ocean. It is dark and fine-grained because it cooled in the open air or under water in months to decades rather than millennia, leaving crystals too small to see.
How it wears
Faster than most hard rock, and generously — it is full of iron, magnesium and calcium, which are exactly what plants want. The iron rusts, so weathered basalt goes red-brown at the surface.
What it means above ground
Deep, dark, fertile soil where it has had time to rot, and stepped terraces and cliffs where flows stacked one on another. Basalt country is famously good farmland once the rock has broken down.
Below, layer 23 million years oldNeither way
Basalt
Quaternary basalt · Quaternary
What it is
The commonest rock on Earth's surface, and the floor of every ocean. It is dark and fine-grained because it cooled in the open air or under water in months to decades rather than millennia, leaving crystals too small to see.
How it wears
Faster than most hard rock, and generously — it is full of iron, magnesium and calcium, which are exactly what plants want. The iron rusts, so weathered basalt goes red-brown at the surface.
What it means above ground
Deep, dark, fertile soil where it has had time to rot, and stepped terraces and cliffs where flows stacked one on another. Basalt country is famously good farmland once the rock has broken down.
Below, layer 33 million years oldNeither way
Basalt
Igneous: extrusive; Extrusive: mafic · Quaternary
What it is
The commonest rock on Earth's surface, and the floor of every ocean. It is dark and fine-grained because it cooled in the open air or under water in months to decades rather than millennia, leaving crystals too small to see.
How it wears
Faster than most hard rock, and generously — it is full of iron, magnesium and calcium, which are exactly what plants want. The iron rusts, so weathered basalt goes red-brown at the surface.
What it means above ground
Deep, dark, fertile soil where it has had time to rot, and stepped terraces and cliffs where flows stacked one on another. Basalt country is famously good farmland once the rock has broken down.
Below, layer 466 million years oldNeither way
Basalt
Cenozoic volcanic rocks · Tertiary
What it is
The commonest rock on Earth's surface, and the floor of every ocean. It is dark and fine-grained because it cooled in the open air or under water in months to decades rather than millennia, leaving crystals too small to see.
How it wears
Faster than most hard rock, and generously — it is full of iron, magnesium and calcium, which are exactly what plants want. The iron rusts, so weathered basalt goes red-brown at the surface.
What it means above ground
Deep, dark, fertile soil where it has had time to rot, and stepped terraces and cliffs where flows stacked one on another. Basalt country is famously good farmland once the rock has broken down.

Bedrock and soil figures are modelled from national geological surveys and global soil mapping, at a resolution of a few hundred metres — right for the shape of a district, not for a particular garden. River discharge is modelled, not gauged. For anything that matters, dig a hole and look.

The field note for Reykjavík, every week

One email, Sunday evening. Unsubscribe anytime.

The ground under Reykjavík

Capital Region · Nordic & Baltic Boreal · basalt country

Try it

Dig down under Reykjavík

Drag the spade down, or tap Dig deeper, through the leaves, the living topsoil and the subsoil, all the way to the bedrock that is really down there.

About 0 cm down

The grass

the top of the ground

Under the grass is a whole hidden world. Drag the spade down — or press Dig deeper — to find out what is down there.

Layer 0 of 5

It takes hundreds of years to make one centimetre of topsoil. The depths are typical — every place is different — and the ruler is squashed at the bottom so the rock fits on the screen.

Say it like this

Age 2“Dig, dig, dig! Who lives down there? A wiggly worm!”
Age 4“Leaves, dark soil, lighter soil, broken rock, solid rock. Can you count the layers? Five!”
Age 6“Topsoil is made of rotted leaves and tiny bits of broken rock. Why do you think it takes hundreds of years to make?”

Go outside: Dig a small hole in the garden and count how many worms live in one shovelful — then put them all back and fill it in.

Try it

Dig down under Reykjavík

Drag the spade down, or tap Dig deeper, through the leaves, the living topsoil and the subsoil, all the way to the bedrock that is really down there.

About 0 cm down

The grass

the top of the ground

Under the grass is a whole hidden world. Drag the spade down — or press Dig deeper — to find out what is down there.

Layer 0 of 5

It takes hundreds of years to make one centimetre of topsoil. The depths are typical — every place is different — and the ruler is squashed at the bottom so the rock fits on the screen.

Say it like this

Age 2“Dig, dig, dig! Who lives down there? A wiggly worm!”
Age 4“Leaves, dark soil, lighter soil, broken rock, solid rock. Can you count the layers? Five!”
Age 6“Topsoil is made of rotted leaves and tiny bits of broken rock. Why do you think it takes hundreds of years to make?”

Go outside: Dig a small hole in the garden and count how many worms live in one shovelful — then put them all back and fill it in.

The river right now

Water near Reykjavík is running high

146%

of the ten-year median for this date · 6.3 m³/s against 4.3 normally

high

drynormal for the dateflood

Under your feet

Reykjavík sits on basalt

About 66 million years old — after the dinosaurs, as mammals and grasslands spread.

All the kinds of rock, and how each one forms →

At the surface66 million years oldNeither way
Basalt
Tertiary-Quaternary volcanic: mafic rocks · Tertiary
What it is
The commonest rock on Earth's surface, and the floor of every ocean. It is dark and fine-grained because it cooled in the open air or under water in months to decades rather than millennia, leaving crystals too small to see.
How it wears
Faster than most hard rock, and generously — it is full of iron, magnesium and calcium, which are exactly what plants want. The iron rusts, so weathered basalt goes red-brown at the surface.
What it means above ground
Deep, dark, fertile soil where it has had time to rot, and stepped terraces and cliffs where flows stacked one on another. Basalt country is famously good farmland once the rock has broken down.
Below, layer 23 million years oldNeither way
Basalt
Quaternary basalt · Quaternary
What it is
The commonest rock on Earth's surface, and the floor of every ocean. It is dark and fine-grained because it cooled in the open air or under water in months to decades rather than millennia, leaving crystals too small to see.
How it wears
Faster than most hard rock, and generously — it is full of iron, magnesium and calcium, which are exactly what plants want. The iron rusts, so weathered basalt goes red-brown at the surface.
What it means above ground
Deep, dark, fertile soil where it has had time to rot, and stepped terraces and cliffs where flows stacked one on another. Basalt country is famously good farmland once the rock has broken down.
Below, layer 33 million years oldNeither way
Basalt
Igneous: extrusive; Extrusive: mafic · Quaternary
What it is
The commonest rock on Earth's surface, and the floor of every ocean. It is dark and fine-grained because it cooled in the open air or under water in months to decades rather than millennia, leaving crystals too small to see.
How it wears
Faster than most hard rock, and generously — it is full of iron, magnesium and calcium, which are exactly what plants want. The iron rusts, so weathered basalt goes red-brown at the surface.
What it means above ground
Deep, dark, fertile soil where it has had time to rot, and stepped terraces and cliffs where flows stacked one on another. Basalt country is famously good farmland once the rock has broken down.
Below, layer 466 million years oldNeither way
Basalt
Cenozoic volcanic rocks · Tertiary
What it is
The commonest rock on Earth's surface, and the floor of every ocean. It is dark and fine-grained because it cooled in the open air or under water in months to decades rather than millennia, leaving crystals too small to see.
How it wears
Faster than most hard rock, and generously — it is full of iron, magnesium and calcium, which are exactly what plants want. The iron rusts, so weathered basalt goes red-brown at the surface.
What it means above ground
Deep, dark, fertile soil where it has had time to rot, and stepped terraces and cliffs where flows stacked one on another. Basalt country is famously good farmland once the rock has broken down.

The field note for Reykjavík, every week

One email, Sunday evening. Unsubscribe anytime.