Major tectonic plate formed by the fusion of the Indian and Australian plates
Map showing the Indo-Australian Plate (IA) and other major plates
The Indo-Australian Plate, shown as its two subdivisions: the
Indian Plate
(red) and the
Australian Plate
(orange)
The
Indo-Australian Plate
is a
major tectonic plate
that includes the
continent of Australia
and the surrounding
ocean
and extends north-west to include the
Indian subcontinent
and the adjacent waters. It was formed by the fusion of the
Indian
and the
Australian
plates approximately 43 million years ago.
[1]
The fusion happened when the
mid-ocean ridge
in the
Indian Ocean
, which separated the two plates, ceased spreading.
[2]
Contemporary models suggest at present there is a deformation zone between the Indian and Australian plates with both earthquake and
global satellite navigation system
data indicating that India and Australia are not moving on the same vectors northward.
[3]
[4]
These observations are consistent with earlier evidence that the Indian Plate and Australian Plate have been acting as separate plates for at least the last 3 million years.
[5]
In due course, some expect a localized boundary to reform between the Indian and Australian plates.
[6]
Regions
[
edit
]
Australia-New Guinea
(
Mainland Australia
,
New Guinea
, and.
Tasmania
), the
Indian subcontinent
, and
Zealandia
(
New Caledonia
,
New Zealand
, and
Norfolk Island
) are all fragments of the ancient
supercontinent
of
Gondwana
. As the
ocean floor
broke apart, these land masses fragmented from one another, and for a time these centers were thought to be dormant and fused into a single plate. However, research in the early 21st century indicates
plate separation of the Indo-Australian Plate
may have already occurred.
[5]
[3]
[6]
[4]
Characteristics
[
edit
]
The eastern side of the plate is the
convergent boundary
with the
Pacific Plate
. The Pacific Plate sinks below the Australian plate and forms the
Kermadec Trench
and the island arcs of
Tonga
and
Kermadec
. New Zealand is situated along the southeastern boundary of the plate, which with New Caledonia makes up the southern and northern ends of the ancient landmass of
Zealandia
, which separated from Australia 85 million years ago. The central part of Zealandia sank under the sea.
The southern margin of the plate forms a
divergent boundary
with the
Antarctic Plate
. The western side is subdivided by the
Indian Plate
that borders the
Arabian Plate
to the north and the
African Plate
to the south. The northern margin of the Indian Plate forms a convergent boundary with the
Eurasian Plate
, which constitutes the active orogenic process of the
Himalayas
and the Hindukush mountains.
The northeast side of the Australian Plate forms a subduction boundary with the Eurasian Plate in the
Indian Ocean
between the borders of
Bangladesh
and
Burma
and to the southwest of the Indonesian islands of
Sumatra
and
Borneo
. Along the northern
Ninety East Ridge
under the Indian Ocean there appears to be a weakness zone where the Indian and Australian plates are going different ways.
[3]
[4]
The subsidence boundary through
Indonesia
is reflected in the
Wallace line
.
Plate movements
[
edit
]
The eastern part (
Australian Plate
) is moving northward at the rate of 5.6 cm (2.2 in) per year while the western part (
Indian Plate
) is moving only at the rate of 3.7 cm (1.5 in) per year due to the impediment of the Himalayas. In terms of the middle of India and Australia's landmasses, Australia is moving northward at 3 cm (1.2 in) per year relative to India.
[3]
This differential movement has resulted in the compression of the former plate near its centre at Sumatra and the division into the separate Indian and Australian plates again.
[7]
[4]
A third plate, known as the
Capricorn Plate
, may also be separating off the western side of the Indian Plate as part of the continued breakup of the Indo-Australian Plate.
[8]
Separation
[
edit
]
Recent studies, and evidence from seismic events such as the
2012 Indian Ocean earthquakes
, suggest that the Indo-Australian Plate may have broken up into two or three separate plates due primarily to stresses induced by the collision of the Indo-Australian Plate with Eurasia along what later became the
Himalayas
,
[9]
[10]
and that the
Indian Plate
and
Australian Plate
may have been separate since at least
3
million years ago
.
[5]
References
[
edit
]
- ^
"The Indo-Australian Plate"
.
austhrutime.com
.
- ^
Keep, Myra; Schellart, Wouter P. (2012). "Introduction to the thematic issue on the evolution and dynamics of the Indo-Australian plate".
Australian Journal of Earth Sciences
. 59, 2012 (6: THEMATIC ISSUE ? Evolution and dynamics of the Indo-Australian plate): 807?808.
Bibcode
:
2012AuJES..59..807K
.
doi
:
10.1080/08120099.2012.708360
.
S2CID
128996831
.
- ^
a
b
c
d
Delescluse, Matthias; Chamot-Rooke, Nicolas (2007).
"Instantaneous deformation and kinematics of the India?Australia Plate"
.
Geophysical Journal International
.
168
(2): 818?842.
doi
:
10.1111/j.1365-246X.2006.03181.x
.
- ^
a
b
c
d
Delescluse, Matthias; Chamot-Rooke, Nicolas; Cattin, Rodolphe; Fleitout, Luce; Trubienko, Olga; Vigny, Christophe (26 September 2012). "April 2012 intra-oceanic seismicity off Sumatra boosted by the Banda-Aceh megathrust".
Nature
.
490
(7419): 240?4.
Bibcode
:
2012Natur.490..240D
.
doi
:
10.1038/nature11520
.
PMID
23023134
.
S2CID
205230868
.
- ^
a
b
c
Stein, Seth; Sella, Giovanni; Okai, Emile A. (2002).
"The January 26, 2001 Bhuj Earthquake and the Diffuse Western Boundary of the Indian Plate"
(PDF)
.
Plate Boundary Zones
. Geodynamics Series. American Geophysical Union. pp. 243?254.
doi
:
10.1029/GD030p0243
.
ISBN
9781118670446
. Retrieved
26 December
2015
.
- ^
a
b
Yue, H.; Lay, T.; Koper, K. (2012). "En echelon and orthogonal fault ruptures of the 11 April 2012 great intraplate earthquakes".
Nature
.
490
: 245?249.
doi
:
10.1038/nature11492
.
- ^
"Earth cracking up under Indian Ocean"
. New Scientist. 26 September 2012
. Retrieved
14 March
2018
.
- ^
Siegel, Lee (26 September 2012).
"Sumatra quake was part of crustal plate breakup: Study shows huge jolt measured 8.7, ripped at least 4 faults"
.
Phys.Org
. Retrieved
6 October
2012
.
- ^
"Press Release: An Earth Plate Is Breaking in Two"
.
www.columbia.edu
.
- ^
R. R. Hillis, R. D. Muller.
Evolution and Dynamics of the Australian Plate