Himalayan range emerged from the Tethys ocean
Alps, Carpathian in Europe, Hindukush in Afganistan to the west of Himalaya
and mountains of Burma in the east,----millions of years ago it all were part of a great ocean Tethys.
The Sea floor of the Tethys ocean was raised up by the collision
to for the Himalayas. That is why you can find sea shell fossils on the top of
Mount Everest! This is a destructive plate margin.
Continent to north to Tethys was Northern Pangea (Laurasia/Angaraland)
and continent to south was Southern Pangea (Gondwanaland).
Various geological factors caused Tethys ocean to come up above the water level.
This water scattered in the lower part of Gondwanaland.
Gondwanaland looked fragmented in parts
and so Indian Ocean came in existence.
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At one time, the Indian craton was a segment of the
Pangaea
supercontinent. During that period, it was linked with Southern Africa
and Madagascar on the southwestern shore and Australia beside the
eastern shore. During the Jurassic era, at approximately 160 Ma (ICS
2004), fissuring led Pangaea to split into two supercontinents i.e.
Laurasia (in the north) and Gondwana (in the south). However, the Indian
craton stayed linked to Gondwana till the supercontinent started to
split into pieces approximately in the beginning phase of the Cretaceous
era around 125 Ma (ICS 2004). The tectonic plate of India started
moving to the north in the direction of the Eurasian plate. This
geological process, which is going on at present, is associated
with the sealing of the Tethys Ocean. The Tethys Ocean’s sealing had
resulted in formation of the Caucasian Mountain Range in West Asia and
the Alps in Europe. It also formed the Tibetan highland in South Asia
and the
Himalayan Mountain Ranges.
pic courtesy: http://science.taskermilward.org.uk/mod1/KS4Chemistry/AQA/Module2/10_2_15.htm |
#reference for classification of Indian rocks:http://www.thecsatupsc.com/2013/04/classification-of-indian-rocks.html
Geological history of India based on rock types
The Geological History of India
began with the geographical transformation of other parts of the earth,
to be precise, 4.57 Ga (billion years back).
India is famous for its
varied geological features.
Various parts of India are made up of rocks
of all categories of several geologic periods.
A few of the rocks are
poorly malformed and metamorphosed.
At the same time, other types of
rocks are newly silted alluvial soils that are still to go through
chemical and physical changes.
Source of minerals of significant
diversity is seen in the subcontinent area in substantial amount.(text courtesy:http://www.mapsofindia.com/500-things-to-know-about-india/geological-history-of-india/)
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Map of chronostratigraphic divisions of India
There are three types of rocks: igneous, metamorphic, and sedimentary. The first two are formed under conditions of extreme heat and pressure.
Igneous rocks are formed when magma
cools into solid form. This can happen on the surface with volcanic
discharge, but primarily takes place beneath the earth’s crust. A majority — about 90% — of igneous rocks are silicate minerals, which are rich in silicon and oxygen. Quartz is among the most familiar and abundant of this type; clays and feldspar are other examples.
Metamorphic rocks are formed when a preexisting rock, called a protolith,
is under conditions of high heat and pressure, causing it to
metamorphose chemically, structurally, or both. The protolith might be
an igneous, sedimentary, or another metamorphic rock. Slate, marble,
and quartzite are some examples of this type.
Sedimentary
rocks are less abundant than the other two varieties, composing only 5%
or so of the earth’s crust. This type of rock is formed over long
periods of time as tiny grains of
material are pressed against each other and join loosely. The process
by which sedimentary rocks are formed is delicate enough that fossils
can be preserved within them. Common examples include sandstone, chalk, and limestone.
picture credit:http://en.wikipedia.org
text credit:http://www.wisegeek.org/what-are-the-different-types-of-rocks.htm
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Geology and major structures of Himalayas
picture credit:http://www.geo.arizona.edu/geo5xx/geo527/Himalayas/geology.html |
Three clear regions of India based on rock types
The geological history of India, it ranges from most archaic to most newly formed rock types.
As rocks date back to Pre Archaen and Pre Cambrian period, their age could well be compared with the age of India itself.
The latest rocks of Quarternary period are found in alluvial deposits (in the form of layer after layer deposits).
The three divisions based on rock types are as follows:
1. A substantial territory of peninsular India, which is also known as the
Indian Shield, comprises schists and Archean gneisses and these are the
earliest forms of rocks seen in India. These are 'original' rocks, made by cooling of the Earth from molten phase. This is part of the Gondwanaland.
2. Rocks of Himalayan mountain and newly formed other moulded related mountain range which are formed later to the rocks of peninsular India, is called Tertiary rocks. Such rocks were formed of the deposits from the base of the ocean.
3. Indo-Gangetic basin , which were formed later to Himalayan mountain range, are Quarternary rocks formed by the alluvial deposits of alluvial soil. This soil is worn down from the Himalayas by rivers originating from Himalayan mountain range.
Above three physical regions of India were formed gradually one after other.
Rock type reserve
Archaic Archean rocks are best for Iron and Gold reserve while rocks of Carboniferous period are known for Coal reserve.
There are more chances of finding mineral oil in rocks formed by the precipitates of ocean.
Himalayan rivers are older than Himalayas
There are two major river systems in India based on the origin:
1.Himalayan Rivers: These rivers are again subdivided into two groups. Trans Himalayan and
Himalayan. The Trans-Himalayan Rivers originate beyond the Great
Himalayas. These are the Indus, the Sutlej and the Brahmaputra rivers.
Himalayan rivers are those which originate in the Himalayas and flow
through the Northern Plains, e.g., the Ganga, the Yamuna and their
tributaries. These rivers are useful for irrigation and navigation and
the lowlands drained by them have fertile alluvial deposits.
The main Himalayan river systems are the
Ganga, the
Indus and the Brahmaputra river systems. The Himalayan rivers form large
basins. Many rivers pass through the Himalayas. These deep valleys with
steep rock sides were formed by the down - cutting of the river during the
period of the Himalayan uplift. They perform intense erosional activity up
the streams and carry huge load of sand and silt. In the plains,
they form large meanders, and a variety of depositional features like flood
plains, river cliffs and levees.
These rivers are perennial as they
get water from the rainfall as well as the melting of ice. Nearly all of
them create huge plains and are navigable over long distances of their
course. These rivers are also harnessed in their upstream catchment area to
generate
hydroelectricity.
2.Peninsular rivers: The main peninsular river systems include the
Narmada, the
Tapti, the Godavari, the Krishna, the Kaveri and the Mahanadi river systems.
The Peninsular rivers flow through shallow valleys. A large number of them
are seasonal as their flow is dependent on rainfall. The intensity of
erosional activities is also comparatively low because of the gentler slope.
The hard rock bed and lack of silt and sand does not allow any significant
meandering. Many rivers therefore have straight and linear courses. These
rivers provide huge opportunities for hydro-electric power.
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| Image Courtesy : gsabulletin.gsapubs.org/content/122/3-4/336/F1.large.jpg |
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| Pic courtesy: http://www.mapsofindia.com/maps/india/geographical.htm |
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| source: www.wikimedia.org |
*author extends thanks to Ms Padmavati Pandey for her valuable input and meaningful discussions during the preparation of this post.
#Find out where an earthquake has occurred today !!
http://www.iris.edu/hq/sis/data/seismon
#reference for Indian rivers in nutshell: http://www.winentrance.com/general_knowledge/geography/rivers.html
