Lesson 4: Classification of Rocks

Rocks

is a naturally occurring aggregate or combination of minerals and mineraloids such as fossils and glass.

Rocks are classified by how?

they are formed, their composition, and texture.

Earth's lithosphere is made primarily of?

rocks and containing one or more minerals in them.

Rocks are constantly being transformed. generated, and destroyed in a process called?

rock cycle

Classification of Rocks

Igneous Rocks, Sedimentary, Metamorphic

Igneous Rock

begins as magma-is formed through the cooling of magma(Magma in a mixture of many minerals.) or lava The term "igneous" is based from the Latin ignis, which means fire.

MAGMA

is a molten sock material beneath the surface of the earth.

Lava

is molten rock material extruded to the surface of the earth through a central vent (volcano) or as fissure eruption.

Igneous Rock classification by composition

Felsic, Mafic

Felsic Igneous Rock

light colored rocks that are rich in elements such as aluminum, potassium, silicon, and sodium. Granite, Rhyolite.

Mafic Igneous Rock

dark colored rocks that are rich in calcium, iron, and magnesium, poor in silicon. Basalt, Gabbro.

Igneous Rock classification by texture

Coarse-grained texture, fine-grained texture

Coarse-grained

take longer to cool more time to grow crystals. Granite, Gabbro.

Fine-grained

cools quickly little to no crystals. Rhyolite, Basalt

Intrusive igneous rocks

magma pushes into surrounding rock below the Earth's surface,cools slowly with larger crystal formation. Granite, diorite, gabbro, pegmatite, and peridotite are examples of this type of rock.

Extrusive igneous rocks

forms when magma erupts onto the Earth's surface (lava), cools quickly with very small or no crystals formed. Other examples of this type of rock are andesite, basalt, dacite, obsidian, pumice, rhyolite, and tuff.

Obsidian

is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form.

Abundant Igneous rocks in the Philippines

andesite, gabbro and basalt.

The famous Taal Volcano has

basaltic rocks

Mayon has both

basalt and andesite

Hibok-Hibok

has andesite only.

Petrology

branch of geology focused on the study of rocks, including their composition, texture, structure, origin, and how they form and change under various conditions.

Sedimentary

weathering of rocks, erosion, sediment transport and deposition (compaction and cementation). Sediments are moved from one place to another. are deposited in layers, with the older ones on the bottom. The layers become compacted and cemented together. are formed at or near the Earth's surface. No heat and pressure involved

Stratification

process arranged in layers

Strata

layers of rocks

Types of sedimentary rocks

Clastic, Chemical, and Organic

Clastic sedimentary rock

made of fragments of rock cemented together with calcite or quartz. Grains, matrix and cement are the components of this type of sedimentary rock. Examples are breccia, conglomerate, sandstone, siltstone, and shale. Fragments cemented together calcite or quartz.

Chemical sedimentary rock

minerals crystallize out of solution to become rock. Examples of these are rock salt, iron ore, chert, flint, some dolomites.

Limestone

in a sedimentary rock composed primarily of calcium carbonate (CaCO) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters.

Organic sedimentary rock

It is formed from the build-up of plant or animal

debris. Examples of this type are coal and fossiliferous limestone. It is usually an organic sedimentary rock that forma from the accumulation of shell, coral, sigal and fecal debra.

Coal

is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment.

In the Philippines,

Limestone is the most abundant found primarily in Chocolate Hills, Bohol, the Kapurpurawan Rock Formation in Burgos, Ilocos Norte and El Nido, Palawan Rocks

Correct format

weathering, erosion, deposition, compaction, cementation

Metamorphic rock ”change in shape”

from existing rock types called “parent rock” in the process called metamorphism, which means a change in form. Are formed from the exposure of sedimentary or igneous rocks to high pressure, high temperature, or both deep within the earth's surface. This process affects the mineralogy and the texture of the rock.

Contact Metamorphism

heated by nearby magma. Increased temperature changes the composition of the rock, minerals are changed into new minerals

Hornfels

is a fine-grained non-foliated metamorphic nick produced by contact metamorphism.

Regional Metamorphism

pressure builds up in rocks that is deep within the Earth. Large pieces of the Earth's crust collide and the rock is deformed and chemically changed by heat and pressure

Metamorphic rocks can be classified into:

Foliated metamorphic rock, Non-foliated metamorphic rocks

Foliated metamorphic rock

contain aligned grains of flat minerals. It typically contains abundant quarts or feldspar minerals. It is formed through pressure due to compression of rocks that create bands called foliation. Examples are gneiss, phyllite, schist, and slate.

Gneiss

is foliated metamorphic rock that has a banded and is appearance made up of granular mineral graina.

Non-foliated metamorphic rocks

It has no foliation or bands. Examples of this type are hornfels, marble, quartzite, and novaculite. Non-Foliated-mineral grains are not arranged in plains or bands

Marble

non-foliated metamorphic rock that is produced from the metamorphism of limestone. It is composed primarily of calcium carbonate.

Mineralogy

the scientific study of minerals, encompassing their chemical composition, crystal structure, physical properties, occurrence, and formation

mineralogist

is a scientist who studies minerals, which are naturally occurring, inorganic solids with a defined chemical composition and crystal structure. Their work encompasses the formation, occurrence, properties, classification, and identification of minerals.