Rock and earth.
Earth is a rocky planet, unlike gas giants such as Jupiter.
It is made of rocks and metal ores.
Earth’s mass is 5.97 × 10²⁶ kg.
Its density is 5.2 g/cm³, making it the densest planet in our solar system.
Structure of the Earth
The core is made mainly of iron.
Around the core is the mantle, which is rock.
Humans can use only the outermost layer above the mantle — this is where rocks and minerals are found.
Limited Resources
Even though Earth has a lot of rocks and minerals, they are still limited.
Extracting them can cause environmental problems.
Some important resources, like coal, may run out in the future.
Peak Mineral Concept
Peak mineral means the time when we extract the maximum amount of a mineral. After that, extraction will decrease.
Peak coal is the point when coal production reaches its highest level.
No one knows exactly when this will happen because we don’t know how much coal is left.
Some say peak coal is 200 years away, while others believe it could happen very soon, even around 2020.
Peak Oil and Other Resources
Peak Oil Prediction
In 1956, M.K. Hubbert — the scientist who created the peak mineral idea — predicted that the USA’s peak oil would happen in 1970.
This prediction turned out to be wrong, because US oil production is still increasing even today.
Finite Resources
All major natural resources are limited and will eventually decline.Estimated peak dates for some important minerals:
Phosphorus → around 2030
Copper → around 2040
Uranium → around the 2030s
These show that many materials we depend on will not last forever.
Why It Matters
Because these resources are finite, it is important to:
Reduce how much we use
Reuse materials whenever possible
Recycle materials to prevent waste
This helps protect the environment and ensures resources last longer.
Early Formation of Earth
Earth was formed around 4.5 billion years ago.
Gravity pulled the heavier elements (like iron) toward the centre, creating the core.
Formation of the Crust
The lighter elements rose to the surface.
These formed the Earth’s crust about 3–4 billion years ago.
Formation of the Mantle
A layer called the mantle formed between the dense core and the light crust.
This three-layer structure — core, mantle, crust — still exists today.