Rock CycleRock CycleCVE 3205CVE 3205

Engineering GeologyEngineering GeologyWong Jee KhaiWong Jee Khai

The Rock CycleThe Rock Cycle• The nature and appearance of a rock is

strongly influenced by the minerals that compose it.

• A rock’s texture – size, shape, and or arrangement of its constituent minerals also has significant effect on its appearance.

The Rock CycleThe Rock Cycle• Rock is any naturally formed, nonliving,

firm and coherent aggregate of mineral matter that constitutes part of a planet.

The Rock CycleThe Rock CycleThe three rock families:1. Igneous rock2. Sedimentary rock3. Metamorphic rock

Igneous rockIgneous rock• Created through the cooling and

solidification of magma• Ignis = fire

Sedimentary rockSedimentary rock• Formed from deposits of sediment• Lithification = conversion into rock

Metamorphic rockMetamorphic rock• Formed by the effects of pressure and

heat on existing rocks

The Rock CycleThe Rock Cycle• The rock cycle describes all the processes by

which rock is:• Formed.• Transported.• Decomposed.• Reformed.• Active volcanoes produce igneous rocks.• Mountain ranges rise as a result of plate

tectonics.• Weathering and erosion change the surface of

the solid Earth.

The Rock CycleThe Rock Cycle• The sediment is buried and compacted,

eventually becoming sedimentary rock.• Deeper burial turns sedimentary rock into

metamorphic rock.• Even deeper burial may cause some of

the metamorphic rock to melt, forming magma from which new igneous rock will form.

The Rock CycleThe Rock CycleEnergy that drives earth’s rock cycle;• Heat from earth’s interior (igneous and

metamorphic rocks)• Sun (sedimentary rocks)

The Tectonic CycleThe Tectonic Cycle• Tectonics is the study of the movement

and deformation of the lithosphere.• When magma rises from deep in the

mantle, it forms new oceanic crust at midocean ridges.

The Tectonic CycleThe Tectonic Cycle• The lifetime of oceanic crust is shorter

than the lifetime of continental crust.• The most ancient oceanic crust of the

ocean basins is only about 180 million years old, and the average age of all oceanic crust is about 70 million years old.

The Tectonic CycleThe Tectonic Cycle• When all oceanic crust sinks back into the

mantle, it carries some water with it.• The water is driven off during volcanic

eruptions.• Some constituents in the hot rock

(calcium, magnesium) are the same as those of seawater.

Geologic Time ScaleGeologic Time Scale• During the nineteenth century, before the

discovery of radioactivity, geologic time scale was developed using principles of relative dating which places the events in proper sequence or order without knowing their age in years.

Geologic Time ScaleGeologic Time Scale• This is done by applying the law of

superposition which states that in layers of sedimentary rocks or lava flows, the youngest layer is on top and the oldest is on the bottom.

Geologic Time ScaleGeologic Time Scale• Fossils are the basis for the principle of

fossil succession, which states that fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil from countless rock layers around the world.