The Shifting Earth - The Darwinian Tourist - page 95

100 mm
per year

EURASIAN
PLATE

40 mm
per year

PACIFIC
PLATE

PHILIPPINE
PLATE

110 mm
per year

INDO-AUSTRALIAN
PLATE

70 mm
per year

Subduction zones

Figure 40 The current confi guration of Indonesia's tectonic plates, with the location of the
2004 earthquake.

By the end of the nineteenth century evidence was accumulating from
geology and the fossil record that the Earth's continents have not always
been in their present positions. For example, nineteenth-century geologists
found fossils of Glossopteris , a little fern-like seed plant, in ancient rocks in
widely scattered locations in South America, Africa, India, and Australia.
Much later, in 1965, Glossopteris was discovered to have thrived in Antarctica . 5
This and other fossil fi nds suggested that all the southern continents had
once been joined together into a single vast landmass, later named Gond-
wana. We now know that Gondwana did exist, and that it began to break up
250 million years ago.
Many such otherwise inexplicable observations were brought together
by the German geologist and explorer Alfred Wegener in 1915. Wegener
concluded that the continents must have drifted somehow to their present
positions, but his theory of continental drift was derided by geologists who
pointed out that there was no obvious mechanism by which such gigantic
masses of rock might have moved.
In 1927 English geologist Arthur Holmes suggested how the continents
might have performed their trick. Holmes proposed a dynamic theory of
tectonic plates (tectonic comes from the Greek for “builder”). He suggested