AMENODING BIATAN HUMMS 5 DATE: 11/03/20
IGNEOUS ROCKS
1. In 1902, a group of American petrographers proposed that all existing
classifications of igneous rocks should be discarded and replaced by a
"quantitative" classification based on chemical analysis. They showed how
vague, and often unscientific, much of the existing terminology was and argued
that as the chemical composition of an igneous rock was its most fundamental
characteristic, it should be elevated to prime position.
2. IGNEOUS: Igneous rocks form as molten rock cools and solidifies. Two
environments are distinguished:
underground - in which case the melt is called 'magma' and the rock that
results from its solidification is described as 'intrusive'.
on the surface - in which case the melt is called 'lava' and the rock that results
are described as 'extrusive' or 'volcanic'.
3. Texture is an important criterion for the naming of volcanic rocks.
The texture of volcanic rocks, including the size, shape, orientation, and
distribution of mineral grains and the interbrain relationships, will determine
whether the rock is termed a tuff, a pyroclastic lava or a simple lava.
However, the texture is only a subordinate part of classifying volcanic rocks, as
most often there needs to be chemical information gleaned from rocks with
extremely fine-grained groundmass or from airfall tuffs, which may be formed
from volcanic ash.
4. igneous rocks have a wide variety of uses. One important use is as stone for
buildings and statues. Diorite was used extensively by ancient civilizations for
vases and other decorative artwork and is still used for art today (Figure 1).
Granite (figure 2) is used both in building construction and for statues.
5. Oligocene to early Miocene igneous rocks are preserved in both the Baguio
district and the Cagayan Valley basin in northern Luzon but porphyry-related
Cu-Au mineralization is currently only known to be associated with rocks of
that age in the Cagayan Valley.
AMENODING BIATAN HUMMS 5 DATE: 11/03/20
SEDIMENTARY ROCKS
1. sedimentary rocks are formed when sediment is deposited out of air,
ice, wind, gravity, or water flows carrying the particles in suspension.
This sediment is often formed when weathering and erosion break down
a rock into loose material in a source area.
2. SEDIMENTARY: Sedimentary rocks form as grains of sediment are
attached to each other by a cement or by the interlocking of grains. The
environment in which this occurs is at or close to the earth's surface and
is characterized by relatively low temperatures and pressures.
3. the size, form and orientation of clasts (the original pieces of rock) in a
sediment is called its texture. The texture is a small-scale property of a
rock, but determines many of its large-scale properties, such as
the density, porosity or permeability.[10]
4. Oil, natural gas, coal, and uranium, our major energy resources, are
formed in and come from sedimentary rocks. Sand and gravel
for construction come from sediment. Sandstone and limestone are used
for building stone. Rock gypsum is used to make plaster.
5. On the other hand, sedimentary rocks are found quite often in
the Philippines also. For example, the Chocolate Hills in Bohol, a city in
the Philippines, is made from limestone, which is a type of sedimentary
rock, as stated on blogs.melb.edu.au.
AMENODING BIATAN HUMMS 5 DATE: 11/03/20
METAMORPHIC ROCKS
1. Metamorphic rocks started out as some other type of rock, but have been
substantially changed from their original igneous, sedimentary, or
earlier metamorphic form. Metamorphic rocks form when rocks are subjected
to high heat, high pressure, hot mineral-rich fluids or, more commonly, some
combination of these factors.
2. METAMORPHIC: Metamorphic rocks form as pre-existing rocks respond to a
radical change in environment, most commonly an increase in temperature,
pressure, and/or an infusion of hot, mineralized fluids.
3. Textures are separated into foliated and non-foliated categories. Foliated rock
is a product of differential stress that deforms the rock in one plane,
sometimes creating a plane of cleavage. For example, slate is a foliated
metamorphic rock, originating from shale. Non-foliated rock does not have
planar patterns of strain.
4. Quartzite and marble are the most used metamorphic rocks. They are
frequently chosen for building materials and artwork. Marble is used for statues
and decorative items like vases (Figure). Quartzite is very hard and is often
crushed and used in building railroad tracks.
5. In the Paolillo Group of Islands (PGI), the oldest rock unit is represented by
ultramafic and related metamorphic rocks found in Bhang Point, northwest of
Paolillo Island and in Jamail Island.
