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1. Tolentino, Alfred John
CMB 1Y1-7
The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into
metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock.
Metamorphic rock can change into igneous or sedimentary rock.
Igneous rock forms when magma cools and makes crystals. Magma is a hot liquid made of
melted minerals. The minerals can form crystals when they cool. Igneous rock can form
underground, where the magma cools slowly. Or, igneous rock can form above ground, where
the magma cools quickly.
Explaination
When it pours out on Earth's surface, magma is called lava. Yes, the same liquid rock matter
that you see coming out of volcanoes.
On Earth's surface, wind and water can break rock into pieces. They can also carry rock pieces
to another place. Usually, the rock pieces, called sediments, drop from the wind or water to
make a layer. The layer can be buried under other layers of sediments. After a long time the
sediments can be cemented together to make sedimentary rock. In this way, igneous rock can
become sedimentary rock.
All rock can be heated. But where does the heat come from? Inside Earth there is heat from
pressure (push your hands together very hard and feel the heat). There is heat from friction (rub
your hands together and feel the heat). There is also heat from radioactive decay (the process
that gives us nuclear power plants that make electricity).
So, what does the heat do to the rock? It bakes the rock.
Baked rock does not melt, but it does change. It forms crystals. If it has crystals already, it
forms larger crystals. Because this rock changes, it is called metamorphic. Remember that a

2. caterpillar changes to become a butterfly. That change is called metamorphosis. Metamorphosis
can occur in rock when they are heated to 300 to 700 degrees Celsius.
When Earth's tectonic plates move around, they produce heat. When they collide, they build
mountains and metamorphose (met-ah-MORE-foes) the rock.
The rock cycle continues. Mountains made of metamorphic rocks can be broken up and washed
away by streams. New sediments from these mountains can make new sedimentary rock.
The rock cycle never stops.
Types of Rocks
Rocks are not all the same!
The three main types, or classes, of rock are sedimentary, metamorphic, andigneous and
the differences among them have to do with how they are formed.
Sedimentary
Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of
material. Together, all these particles are called sediment . Gradually, the sediment accumulates
in layers and over a long period of time hardens into rock. Generally, sedimentary rock is fairly
soft and may break apart or crumble easily. You can often see sand, pebbles, or stones in the
rock, and it is usually the only type that contains fossils.
Examples of this rock type include conglomerate and limestone.
Metamorphic
Metamorphic rocks are formed under the surface of the earth from the metamorphosis (change)
that occurs due to intense heat and pressure (squeezing). The rocks that result from these
processes often have ribbonlike layers and may have shiny crystals, formed by minerals growing
slowly over time, on their surface.
Examples of this rock type include gneiss and marble.
Igneous
Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens.
Sometimes the magma cools inside the earth, and other times it erupts onto the surface from
volcanoes (in this case, it is called lava). When lava cools very quickly, no crystals form and the
rock looks shiny and glasslike. Sometimes gas bubbles are trapped in the rock during the cooling
process, leaving tiny holes and spaces in the rock.
Examples of this rock type include basalt and obsidian.

3. The Processes of the Rock Cycle
Weathering - is the “in situ” breakdown of rocks at the Earth’s surface, doesn’t involve
transport.
Erosion - is the gradual wearing away of material at the Earth’s surface as it undergoes
transport.
Transport - involves sediment being moved from one place to another. The agents of
transport are wind, water, ice and gravity.
Deposition- occurs due to physical (commonly loss of energy) or chemical changes and
results in material being laid down on the Earth’s surface. One sedimentary bed is the result
of one period of deposition.
Burial - occurs as sediment is covered over as more layers of sediment accumulate on top
(the overburden).
Lithification - the process of converting loose sediment into a sedimentary rock.
Diagenesis - all the physical (mainly compaction) and chemical (mainly cementation)
processes that act on sediment during lithification.
Extrusion occurs when magma is erupted as lavas/pyroclastics onto the Earth’s surface. This
forms a volcanic/extrusive rock.
Intrusion occurs when magma cools and crystallises inside the Earth’s crust. This forms a
plutonic (deep-seated) or hypabyssal (shallow level/near surface) intrusive rock.
Partial Melting is the process by which magma forms in the Earth’s mantle – different
minerals have different melting points so only part of the rocky/silicate mantle melts to form
magma.
Magma accumulation is the process by which the magma collects within an underground
magma chamber.
Crystallisation occurs when molten magma cools and solidifies into individual
crystals/minerals.
Metamorphism is the process by which rocks in the Earth’s crust are changed by the effects
of heat and pressure. The process is isochemical and involves solid state recrystallisation.
Recrystallisation occurs during metamorphism – it is a solid-state process by which existing
minerals are changed/recrystallised into new crystalline metamorphic minerals.
Uplift is the process by which deeply buried rocks are returned to the Earth’s surface by
tectonic forces.