The History and Plants of Palm Valley

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200 million years ago

Australia began as part of a great southern super-continent called Gondwana.
At this time, the climate is luxuriously warm and wet worldwide.

The Earth is covered in rainforest made up of ferns and gymnosperms, including pines and cycads.

45 million years ago

Currents deep within the Earth have caused Gondwana to break up.
Australia is separating from Antarctica and starting to move slowly northward, as it still does today.

The break-up of Gondwana is causing dramatic climate changes and the extinction of many of the old plant and animal groups.
Rainforest still covers much of the Earth, but is made up more of the new angiosperms, the flowering plants: flowering trees and palms have started to dominate over pines, cycads and other gymnosperms.

15 million years ago

Major ice sheets have formed in Antarctica and climates have become cooler and more arid worldwide.

Australia has started to dry out and is now covered mainly by open woodland, with wattles, Casuarinas and some Eucalypts, and grasslands.
Rainforest has mostly retreated to the north and east.

Around 10 million years ago

As Australia collides with Asia, mountains are pushed up in New Guinea and along eastern Australia.
A severe rainshadow forms across inland Australia and central Australia becomes more arid.

2 million years ago

The North Polar ice cap is forming.
With more of the Earth's water tied up in ice, the world has become much drier.

Much of Australia is now semi-arid.
There are patches of rainforest in central Australia, with Acacia (wattle) woodland and grasslands dominating.

Present

During the ice age peak 18,000 years ago, the driest period in Australia's history, vast areas of sand dunes developed in central Australia.

Today, inland Australia is well-vegetated, covered with Acacia woodland, shrubs and grasses.
In central Australia, remnants of the old rainforests, like the cycads and palms, are found only in small, isolated refuges like Palm Valley.

Palm Valley taps into a huge underground basin of fossil water, largely unaffected by present-day droughts.

This sandstone is like a sponge saturated with water.
Water moves very slowly through the sandstone, because of its low permeability.
Most of the water seeping out into Palm Valley, through cracks and other features in the sandstone, is old water, although some is from recent rains.

The Central Australian Red-cabbage Palms

Despite changing conditions, Central Australian Red-cabbage Palms have survived here in the desert, hundreds of kilometres from any other palms.

Palm Valley is one of very few areas in the Central Ranges where there is both permanent water and protection from raging floods.
Water that fell as rain thousands of years ago, when central Australia was much wetter, now seeps down through a great mass of fractured sandstone, towards Palm Valley and beyond.
High valley walls protect the palms from drying winds.
The gentle slope of Palm Creek means that the palms' shallow roots are protected from scouring by great deluges of water.

The MacDonnell Ranges Cycad

The MacDonnell Ranges Cycad (scientific name Macrozamia macdonnellii) only grows in the Central Australian ranges, although other forms of cycad are found elsewhere in Australia.

These cycads grow mainly on rocky slopes where they get some shelter from the hot sun, and where their roots can penetrate deep into moisture-trapping rock crevices.

The cycad is also a very slow growing plant.
Its trunk consists of the densely packed remains of every leaf the plant ever grew.
By counting these leaf bases, scientists estimate that some of the local cycads are 300  years old.
So these individuals were alive and growing here even before captain Cook landed in Australia.

 

 

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Last updated: Tuesday, 21.04.2009 11:52 AM