438 to 390 MILLION YEARS AGO
Extensive shallow seas existed around the Paleo-Tethys Ocean region. This was a good time to permit the growth of massive and widespread coral reefs far greater than the Great Barrier Reef today to flourish.
While oxygen levels were rising above 25 per cent, the actual pressure in the atmosphere had probably risen to about one-tenth of its present-day value, during which time simple plants like Cooksonia started to adapt to the drier environment of land.
The first plants to take hold on land grew initially in marshy land areas with its primitive root system still embedded in the nearby water supply, and then later in the more desert-like expanses inland.
Wingless insects became the first creatures to crawl onto land, following the vegetation ashore, sometime during the end of this period or the early Devonian Period.
420 MILLION YEARS AGO
Glaciation appeared at this time despite high levels of carbon dioxide in the atmosphere. Scientists are not too sure why. Perhaps volcanic eruptions have sent debris high in the upper atmosphere to reduce sunlight?
400 MILLION YEARS AGO
The region where the capital city of Australia is located — Canberra — was once at the bottom of a tropical shallow sea containing reefs, sea shells, corals and beaches along great expanses of land containing volcanoes with plants hugging the shores, rivers and lakes for water and nutrients.
Elsewhere, the places we call Scotland and England were joined together. A mountain range is created over the next 50 millions known as the Highlands.