Shaping the Earth

Updated

18/03/20

Pyroclastic plume on a volcano

Simpson Desert Expedition 2015

Iceberg in Arctic ice floes

What makes the Earth unique? Where does it fit in the Solar System and, ultimately, the universe? Take a look inside the Earth and find out what it is made from and how it is structured. Look at the processes that shape the Earth.

Age, structure and composition of the Earth

Find out about the structures and materials that form our Planet.

Microkrystite spherules

Glossary of geoscience terms

Geoscience (also known as earth sciences and geology) is the study of the Earth and includes all non-living parts of our environment, and everything below the Earth's surface. Here are some common geoscience terms explained.

Earth illustration

Structure and composition of the Earth

The overall composition of the Earth is very similar to that of meteorites, and because of this, it is thought that the Earth originally formed from Planetesimals composed largely of metallic iron and silicates.

Clay wall close up

Looking inside the Earth

The internal structure of the Earth consists of three main parts, the crust, mantle and core. The division between the crust and the mantle is called the Moho.

Plate Tectonics

Since the 1950s, several discoveries have led to a new understanding of how the Earth works.

Smoky Quartz and Molybdenite

The geological time scale

Historical records only go back a few thousand years, and are inadequate to treat most geological processes.

Radioactive dating

Radioactive dating is a method of dating rocks and minerals using radioactive isotopes. This method is useful for igneous and metamorphic rocks, which cannot be dated by the stratigraphic correlation method used for sedimentary rocks.

Geological ore deposits

Geological ore deposits are of many different types and occur in all geological environments.

Earth's surroundings

Learn about Earth's cosmological environment.

Hubble composite 2012

The universe

The universe can be defined as the whole of existing things from the scale of sub-micron to outer space.

The Solar System

The Solar System is dominated by the Sun and the planets that orbit around it.

Adelie Land Meteorite

Meteors and Meteorites

Solid pieces of extraterrestrial debris (meteoroids) can stray from their orbits in outer space and be captured by Earth's gravity.

Tektites

Tektites are small, pebble-like glassy objects of Earth material that have been melted by meteorite impact, splashed up into our atmosphere, and fallen to Earth again under gravity.

Barratta meteorite

The 'Barratta' Meteorite

The story of the 'Barratta meteorite' has a rather uncertain beginning. One version claims that in 1859 a stockman witnessed spectacular light and sound effects at a place where pieces of the meteorite were later found.

Sedimentary processes and structures

Sediments are formed by the breakdown of pre-existing rocks.

Sedimentary processes

Sedimentary processes

Sediments are formed by the breakdown (both physical and chemical) of pre-existing rocks, which may be of igneous, metamorphic or sedimentary origin.

Simpson Desert Expedition 2015

Sedimentary structures

Sedimentary structures can be of either physical (e.g. wave action) or biological (e.g. disruption of sediments by animals) origin.

Timor-Leste Expedition 2012

Sedimentary environments

Sedimentary environments can be classified according to the climate in which they occur and/or the geometrical arrangement of the sediments.

Classification of sedimentary rocks

Sedimentary rocks are classified according to the predominant grain size present, as well as by their mineral content.

Characteristics of sediments

Sediments can be classified by their characteristics, which relate to how they have been transported and weathered and how far from their original source they have been deposited.

Water and sedimentary transport

Water plays a vital role in most sedimentary processes. Pure water itself has little effect on rocks. It is the dissolved gases in water, particularly carbon dioxide, that cause the chemical decay of minerals and mineral dissolution.

Ishigaki ishigakijima limestone cave

Limestone caves

Caves form in limestone (calcium carbonate), and occasionally in dolomite (calcium magnesium carbonate), when water containing dissolved carbon dioxide (carbonic acid) seeps into rock crevices and joints.

Students visiting Jenolan Caves

Jenolan Caves Minerals

The Jenolan Caves are one of the premier tourist attractions of New South Wales. Nine caves are regularly shown to visitors, but several hundred of various sizes are known from the area.

MA695 Geological relief map of NSW

The Sydney Basin

The Sydney Basin is a major structural basin containing a thick Permian-Triassic (290 Ma - 200 Ma (million years old)) sedimentary sequence that is part of the much larger Sydney-Gunnedah-Bowen Basin.

Soils

Soils are made up of three layers and are thickest where they are older and in warm and wet environments.

Agate Geode Agate Ck Qld

Concretions, Thunder Eggs and Geodes

Concretions are compact, often rounded, accumulations of mineral matter that form inside sedimentary rocks such as shale and sandstone or in soil.

Volcanic and Magmatic processes and structures

Volcanoes create material for rocks and landforms. Igneous rocks are formed by solidification from a molten state.

Structure of volcanoes

Although volcanoes are often seen as being destructive they are also constructive. They add more land to the surface of the Earth and, when weathered, provide us with a nutrient-rich soil for agriculture.

Lavas

One of the products of volcanic eruptions is lava. Lavas vary widely in composition depending upon their original source magma.

Magma

Magma is hot molten mobile rock. Igneous rocks form when magma cools and solidifies. Magmas come out of active volcanoes as lavas.

Aerial view of volcanic eruption

Pyroclastic processes and materials

Pyroclastic means 'fire broken' and is the term for rocks formed from fragments produced by volcanic explosions.

Flow-banded rhyolite

Volcanic rocks

Volcanic rocks are divided into three main types: basaltic, volcaniclastic and pyroclastic.

Hawaiian Volcanic landscape

Volcanic landforms

Each type of volcanic massif (structure) contains lavas, pyroclastic rocks and intrusions, but these differ in proportions and compositions.

Classification of igneous rocks

Igneous rocks are formed when magma cools and solidifies. They are classified by using grain size, silica content, and/or silica saturation.

Igneous rock types

Igneous rocks can be divided up into four groups, based on how they were formed and what they are made of.

Igneous intrusion in Sweden

Igneous intrusions

Molten magma can invade the Earth's upper layers and then solidify as igneous intrusions.

Metamorphic processes and structures

The word metamorphism comes from Greek and means 'change of form'.

Metamorphism

The word metamorphism comes from Greek and means 'change of form'. Metamorphic rocks are pre-existing rocks whose mineral composition and/or texture has been changed by processes within the Earth.

Blueschist - a metamorphic rock

Types of metamorphism

There are several different types of metamorphism, including dynamic, contact, regional, and retrogressive metamorphism, that form and shape rocks.

Metamorphic processes

Most minerals are only stable at particular temperatures and pressures, so changes in these result in the formation of new minerals.

Metamorphic rocks

Metamorphic rocks form because of changes in temperature and depth of burial within the Earth in a solid state without actual melting.