The document describes the three main types of rocks: sedimentary, metamorphic, and igneous. It provides examples of each type and explains their formation processes. Sedimentary rocks form from compressed particles, metamorphic rocks form from intense heat and pressure altering existing rocks, and igneous rocks form from cooling magma. The document also explains the rock cycle, where rocks constantly change forms through weathering, sedimentation, metamorphism, and melting processes.

1. MUNEEBA
FATIMA
M.Sc -ZOW,UoK
MUNEEBA FATIMA
MSC-ZOW,UOK

2. TYPES OF ROCKS
 Rocks are not all the same!
 The three main types, or classes, of rock are sedimentary,
metamorphic, and igneous 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.

3. 
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.

5. ROCK CYCLE
The rock cycle can be described as dynamic.
Why is it important that we learn about the rock cycle?
It is important because it is a vital part of how the earth is changing constantly
and dynamically.
One way to think of the rock cycle is that the rocks are recycling themselves.
Here is the path of one rock.
1. We start in the middle of the earth, in the mantle as magma.
2. We are then shoved to the surface via a volcano as lava.
– When we cool, we are now an igneous rock, basalt.
3. We are slowly weathered down to smaller and smaller parts.
4. Some of our parts wind up at the bottom of a lake.
5. Over time, with pressure, we compress with our friends (other sediments).
-We are now a layered sedimentary rock, sandstone.
6. We are pushed down into the earths crust after layer after layer of rock covers
us.
7. As we are pushed down, heat and pressure increase.
8. The continued pressure transforms the rock.
-We are now a metamorphic rock, marble.
Repeat ∞ times.

6. ROCK CYCLE