The ocean is what makes our planet truly unique. Nowhere else in the solar system is there an ocean of liquid water on the surface. It is the most shifting, changeable place on Earth, but it’s also one of the oldest. The sea was here before life began, and will be long after we’ve gone.
Scientists believe the ocean was formed around 4 billion years ago, and as a surface feature is older than all the surviving continents. The water was born from rocks deep within the earth, and ejected as steam from volcanoes soon after the Earth condensed from its whirling cloud of rock and gas. Some of the water may have been extraterrestrial, arriving as ice with the comets and asteroids.
The oceans have been shifting and shaping the land ever since. New ocean floor formation is one of the main forces behind continental drift: molten rock upwells at the mid-ocean ridges, creating new ocean crust and spreading outwards. Meanwhile, older crust is subducted under continental plates. Despite being 4 billion years old, there are few parts of the ocean floor older than 220 million years.
Margaret River, famous for its massive and spectacular waves, is right on the dynamic junction between the Indian and Southern Oceans. Both are far younger than the land which they lap. For aeons, the south-west of Australia was landlocked near the edge of Gondwana. The coastal granites are a remnant of the time when we were joined to India, facing the ancient Tethys Sea. When Gondwana began to break up, India detached from Africa and drifted north. The Indian Ocean grew in its wake, by means of an ocean ridge spreading and pushing the land mass northward. Eventually India collided with the south of Asia, closing the Tethys Sea.
Then, millions of years later, a new ocean ridge formed between Australia and Antarctica, opening a rift valley between them. The newly formed Indian Ocean surged into the void, making a long and narrow inlet. By 45 million years ago, the two land masses were joined only by a ‘hinge’ between Tasmania and Antarctica. When this was finally breached, Australia began to drift north, and the Southern Ocean was born.
Soon after, South America also drifted north and Antarctica became an island at the south pole, surrounded by the Southern Ocean. The circumpolar current was born, whipping itself up into a wild, wind-driven frenzy and chasing its own tail around the pole. It carries 145 million cubic metres of water from the Indian to the Pacific Ocean every second. The circumpolar current has a major impact on global climate, and you can read all about it in this excellent article from the Australian Antarctic Magazine.
The two oceans off the south-west coast of Australia create an interplay between the tropical north, and the polar south. In summer, the Western Australian current brings cold water north from Antarctica, while the sub-tropical high pressure systems move south and keep the cold fronts of the Southern Ocean at bay. In winter, the Leeuwin current brings warm water down along the coast from the sub-tropics, while the cold fronts venture further north, bringing their gales, rain, and stormy seas to the the edge of the continent. The sea generates our rivers, our rain, our freshwater: the whole of the water cycle depends on it.
The waves that clip the edge of Australia’s south-west are generated by the strongest winds in the world. These waves have a fetch of thousands of kilometres of uninhibited ocean. Their force shapes the coast of Western Australia, carving into it with an infinity of ephemeral force.
The sea has very deep significance for all cultures that have lived or moved by its shores. The sea brings things on its wind and currents, and takes them away. Marine life, driftwood, seaweed, ships. The sea brings infinite inspiration. A symbol of emotional life and the subconscious: those parts of ourselves that shape us, but we can never fully fathom.
Even today, scientists have mapped the Moon in more detail than they have the ocean floor. The great abysses remain one of the mysteries of the Universe. Perhaps that’s why we are so drawn to the sea, into the infinite blue to deepen our experience of self.
Copyright Jinni Wilson 2021