Earth Beneath Our Feet

Earth is made of layers, rather like a peach with a thin skin around its centre. The rocky crust is the surface we live on. It is thinner beneath oceans than beneath continents. Below it, the mantle is a very thick layer of hot rock. Although much of this rock is solid, it can slowly flow over long periods of time. At the centre of Earth are two layers. The outer core is liquid iron and nickel. The inner core is solid iron and nickel. The inner core stays solid because the pressure at Earth's centre is enormous, even though it is extremely hot. The crust and the stiff uppermost part of the mantle form the lithosphere. It is divided into huge sections called tectonic plates. These plates move slowly over a softer, slowly moving part of the upper mantle called the asthenosphere. Heat inside Earth helps drive convection currents: warm material rises and cooler material sinks, moving the mantle and helping shift the plates. Where plates meet are plate boundaries. Plates may move apart, push together, or slide past one another. These movements can build mountains, create new ocean floor, and cause earthquakes. At some boundaries, melted rock called magma can rise and feed volcanoes. Aotearoa New Zealand lies where the Pacific Plate and Australian Plate meet. Their movements help shape the country. The Southern Alps have been lifted as the plates push together, and volcanoes in the central North Island are linked to one plate moving beneath the other. Because plate movements can cause earthquakes and volcanic activity, learning about Earth's layers and boundaries helps people understand hazards and plan ways to stay safe.