Western Australia is the largest state in Australia, covering more than 2.5 million square kilometres. Geological mapping started in the mid-1800s, with geologists observing the land during searches for mineral deposits, water, and farmland. The Geological Survey of Western Australia (GSWA) was established in 1888, when the first full-time Government Geologist was appointed. Systematic mapping began in the 1950s, and by 1980, the entire state had been mapped at 1:250 000 scale. More detailed mapping at 1:100 000 scale began after that and continues today, though the methods used have changed a lot. We choose new mapping projects based on how much they benefit the Western Australian community.
Pre-fieldwork consultation
Before starting a mapping project, we talk to Traditional Owners, pastoralists, and mining companies to make sure we have permission to access the land and respect land ownership. We work with the Department of Biodiversity, Conservation and Attractions, and other government agencies, to identify any environmental concerns.
Fieldwork now and then
In the late 1800s and early 1900s, camels and horses were used during geological expeditions. By the 1920s, motor vehicles began replacing them, while ships and trains were used for longer trips. Planes were occasionally used starting in the 1930s.
Today, we use four-wheel-drive vehicles to reach rock outcrops. We carry camping gear, safety equipment, food, and water. We might move basecamp every few days or camp at different spots each night as we map an area.
Helicopters are sometimes used to reach hard-to-get-to outcrops, especially for collecting samples during large-scale surveys.
On the ground, we use digital photos, satellite images, and GPS to help find outcrops. We take measurements with a compass and record detailed observations directly into a special computer system (GIS) using a rugged tablet built for fieldwork.
Collecting rock and soil samples
We collect rock and soil samples to study them further. Some of the methods we use include:
- Petrography: cutting a thin slice of rock to look at under a microscope, which helps identify the different minerals in the rock.
- Geochronology: extracting key minerals from rocks to determine their age.
- Chemical analysis: measuring the amounts of different elements in the rocks to understand where they came from and their history.
Compiling the data
Map-making is now all done digitally, replacing the old way of drawing and colouring maps by hand. We use GIS software to put together geological data, which helps make maps more accurate. The geological information is plotted on a various basemaps, and the map starts to take shape as we link known rock outcrops where we’ve collected data. Field data is combined with geophysical and satellite information to create a clearer, bigger picture of the geology. A map legend is important because it explains the age, types of rocks, and how the rock layers are related in a specific area.
Samples collected in the field are analysed to find out their composition and age, which helps us understand the area better.
GIS specialists help by checking the digital map for errors and merging new data with old maps to cover more of the State.
Integrating data into maps
The geological map is created by adding the information collected during fieldwork and lab tests onto a map. Today, geophysics, especially detailed aerial magnetic images, are an important part of how we interpret data and create maps.
Up until about 2016, we created traditional geological maps, drawn to specific scales (1:250,000 or 1:100,000). Since the mid-2010s, we stopped printing most of our maps and started releasing new mapping data as downloadable GIS files. These files are available on the Data and Software Centre or through GeoVIEW.WA.
The digital maps include data that you can click on to get more information. For example, if you click on a rock unit in the map, it will show you details like the rock's age, and how it relates to other rocks.
Publishing GSWA maps
Geological maps are now created using computers instead of being printed. These maps show not only rock types and outcrops but also features like creeks, roads, tracks, bores, and mineral deposits. They are often the most accurate maps available because the information is double-checked during the mapping process. Nowadays, geological maps are just one part of a digital data package with many layers of information. Discover GSWA maps through the DEMIRS eBookshop, Data and Software Centre, and GeoVIEW.
