The age of Planet Earth...  Earth is about 4,6 billion years old!  In the beginning Earth consisted of molten metal and rocks.  Heavy metals sunk deeper and lighter metals floated at the top.

Earth is a huge ball and consists of four concentric layers Crust Inner core Outer core Mantle

The crust is a thin layer - almost like the peel of an apple.

MANTLE OCEANIC CRUST CONTINENTAL CRUST

THE CRUST  The crust of the earth looks solid, but moves constantly on the molten mantle.  The crust is divided into huge plates, the tectonic plates.  The crusts of the continents consist of granite and quartz, while the oceanic crust consists of basalt.  The outermost layer of the mantle and the crust form the lithosphere.

Basalt is solidified lava

Granite quarry

Quartz

Tectonic plates HwPR_4mP4&feature=player_detailpage

The rock cycle

Three main types of rock 1. Igneous rock 2. Sedimentary rock 3. Metamorphic rock

Igneous rock  From Greek word meaning „fire”.  Molten rock is called magma.  When magma cools down and solidifies, igneous rock is formed.  Granite forms when magma cools slowly and form big crystals.  Basalt and pumice form when magma cools faster and form small crystals.  Pumice also has many holes – spaces filled with air/ bubbles when still hot.

WE ALL KNOW PUMICE STONE

SEDIMENTARY ROCK – it is difficult to believe that the Karoo was once an inland sea, until you see the koppies and layers of sedimantary rock

Different types of sediment form different types of sedimentary rock

Sedimentary rock  Sedimentary rock forms when rock fragments and mineral particles settle at the bottom of the sea, a lake or a river.  Over time the layers of sand, silt and clay become cemented together under high pressure.  Sandstone, shale and limestone are examples of sedimentary rock.

Weathered sandstone

Metamorphic rock  Metamorphic rock forms when igneous or sedimentary rock are heated or put under high pressure for a long time.  Marble and slate are metamorphic rock types that came from sedimentary rock put under heat and pressure.

Slate rock Slate roofing

Marble  Marble forms when limestone, a sedimentary rock, undergoes heat and pressure.  The main mineral in marble (and limestone) is calcium carbonate (CaCO 3 ), giving it a white colour.  The colours of marble are due to other minerals e.g. red marble contains iron oxide.

White marble quarry in Tuscany Statue of Herakles