Background reading · Science

From the ground up: how we use Earth's resources

Coal, ironsand, limestone, gravel and pounamu all come out of the ground. We choose each one for its properties.

Look around your classroom. The concrete floor, the glass window, the steel roof and the copper wires inside the walls all started as rocks or minerals dug out of the Earth. Natural materials like these are called Earth resources, and many of them are found in deposits: places where one useful material has built up.

Choosing by properties

People choose Earth materials because of what they are like. Some examples:

Iron: strong and dense, so it is made into steel for bridges, nails and roofing. New Zealand makes steel from black ironsand on west coast beaches of the North Island.

Aluminium: strong but light, so it is used for boats, ladders and aircraft.

Coal: stores energy from ancient swamp plants. It burns hot, which is why it has been used in power stations and to make steel, but burning it adds carbon dioxide to the air.

Limestone: made from shells, it is crushed and heated to make cement for concrete, and spread on farms to sweeten sour soil.

Gravel and sand: dug from rivers and quarries for roads, paths and concrete. We use more of these than any other Earth material.

Taonga from the land

Long before steel, Māori knew the properties of stone well. Hard, tough pounamu (greenstone) from Te Waipounamu was shaped into adzes, chisels and precious ornaments. Obsidian, a volcanic glass, made razor-sharp cutting tools and was traded across the country. Today pounamu is a taonga. In most of the South Island, natural pounamu belongs to Ngāi Tahu, so it is not collected without their permission.

Resources do not grow back

Rocks and minerals take millions of years to form, so once we dig them up they are gone. Reusing steel, recycling aluminium cans and choosing long-lasting materials all mean less digging.

Sources and further reading

Written for Kōkiri Learn students in our own words. Check facts against the sources.

Used in: Rocks to Stars: Earth and Space