unit 5-the rocks

7/21/2019 Unit 5-The Rocks

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CIENCIAS NATURALES 1ºESO TEMA 5IES DELGADO HERNANDEZ DEPARTAMENTO DE FÍSICA Y QUÍMICA

UNIT 5: The rocks

VOCABULARY

Here is the vocabulary we are going to use in this unit. You have to look up the

meaning of the missing words and write it down in this table.

WORD MEANING

A rock is made of..... Una roca está hecha de (formada por).......

Absorb Absorber

According to Seg ún

Arrange Arreglar; organizar

Basalt

Bottom Fondo

Build up Acumular

Calcite

Cementation Cementación

Clay

Claystone

Compaction Compactación

Conglomerate

Cycle Ciclo

Derive from Provenir, obtenerse de

Detrital Detrítico

Erupt Entrar en erupción

Extrusive

Fit Ajustar, encajar

Forever Para siempre

Formation Formación

Fossil

Gap Espacio, hueco

Glue Pegamento

Grain

Granite

Gravel Grava

Igneous

Inside (n)interior;(prep)dentro de;(adv)dentro;(adj)interior

Instead En vez de

Interlocking Entrelazado

Intrusive

Lake Lago

Layer

Limestone CalizaLoad Carga

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Marble

Metamorphic

Molten Fundido, líquido

Porous Poroso

Pressure (n)Presión;(v)presionar

Reach Alcanzar

Recycle Reciclar

Remove Quitar, sacar

Rock

Rounded Redondeado

Sand

Sandstone

Sea Mar

Sediment /

Sedimentary /

Sedimentation

Settle Asentarse

Slate

Split Dividir, separar

Soft / softer Blando / más blando

Squash Aplastar

Stick Pegar

Suffer Sufrir

The oldest El más viejo

The youngest El más joven

Trap (n)Trampa;cazar, atrapar

Underground Subterraneo, bajo tierra

Volcano

Weathering

Weight Peso

THEORY

1) What are rocks?

A rock is made of grains that fit together. Each grain in the rock is made from a

mineral, which is a chemical compound. The grains in a rock can be different

colours, shapes and sizes.

Some types of rock have interlocking grains. Granite is a rock with interlocking

grains. Other types of rock have rounded grains. Sandstone is a rock with

rounded grains.

Rocks with rounded grains absorb more water than rocks with interlocking grains.

This is because the water can get into the gaps between the grains. We call rocks

that absorb water porous. Rocks with rounded grains are usually softer than rocks

with interlocking grains.

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2) Sedimentary rocks

A. Detrital

Detrital sedimentary rocks derive from the weathering of pre-existing rocks.

Formation

When a river reaches a lake or the sea, its load of transported rocks settles to the

bottom. The deposited rocks build up in layers, that we call sediments. We call

this process sedimentation.The weight of the sediments on top squashes the sediments at the bottom. We call

this compaction.

The crystals form a glue that sticks the pieces of rock together. We call this process

cementation.

It may take millions of years for sedimentary rocks to form. These are the different

processes in order:

sedimentation --> compaction --> cementation

We classify detrital sedimentary rocks according to their texture (grain size)

Gravel: Grain size greater than 2 mm --> conglomerateSand: Grain size 0.02 to 2 mm --> sandstone

Clay: Grain size less than 0.02 mm --> claystone

CONGLOMERATE CLAYSTONE SANDSTONE

B. Chemical/biochemical Sedimentary Rocks

These rocks derive from chemical components dissolved in the seawater. These

chemicals may be removed from seawater and made into rocks by chemical

processes. Examples of these rocks are rock salt and calcite (limestone).

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CALCITE ROCK SALT

C. Organic Sedimentary Rocks (Coals)

This group consists of rocks composed of organic matter (mainly plant fragments).

These are the coals.

3) Igneous rocks

Formation

The inside of the Earth is very hot - hot enough to melt rocks. Molten (liquid) rock

forms when rocks melt. We call the molten rock magma. When the magma cools

and solidifies, forms igneous rock.

What are they like?

Igneous rocks contain interlocking crystals. The size of the crystals depends

on how quickly the molten magma solidified. If the magma cools quickly,

small crystals form in the rock. This happens when the magma erupts from

a volcano. Basalt is an example of this type of rock. It is an extrusive

igneous rock. If the magma cools slowly, large crystals form in the rock. This

happens if the magma cools deep underground. Granite is an example of

this type of rock. It is an intrusive igneous rock.

BASALT GRANITE

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Unlike sedimentary rocks, igneous rocks do not contain any fossils.

4) Metamorphic rocks

Metamorphic rocks derive from other rocks that change because of heat orpressure.

Formation

Some rocks suffer heat and great pressures and the minerals that they contain

change: we have a metamorphic rock.

Remember that the rocks that form metamorphic rocks do not melt. Those rocks

that do melt, form igneous rocks instead.

What are metamorphic rocks like?

Crystals in metamorphic rocks arrange in layers.

Slate is useful for making roof tiles because its layers can be split into separate

flat sheets.

Marble is another example of a metamorphic rock. It derives from limestone.

Metamorphic rocks sometimes contain fossils.

SLATE MARBLE

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5)The rock cycle

Remember that there are three main types of rock:

• Sedimentary, for example limestone, sandstone and conglomerate;

• Igneous, for example basalt and granite;

• Metamorphic, for example slate and marble

The Earth's rocks do not stay the same forever. They are continually changing

because of processes such as weathering and large earth movements. The rocks

recycle over millions of years. We call this process: the rock cycle.

ACTIVITIES

1) Identify the following rocks:

CARACTERISTIC ROCK

Its layers can be split into separate flat sheets.

They derive from chemical components dissolved in theseawater.

The grain size is between 0.02mm and 2 mm

The magma cools slowly, large crystals form in the rock.

The grain size is smaller than 0.02 mm

It derives from limestone.

The magma cools quickly and small crystals form in the rock.

The grain size is greater than 2 mm

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2) Work in pairs and complete the following sentences with the

right word (or words):

a) A rock is made of __________ that fit togetherb) The Earth's __________ do not stay the same forever

c) __________ is another example of a metamorphic rock

d) Crystals in metamorphic rocks arrange in __________

e) Rocks with __________ absorb more water than rocks with __________.

f) The weight of the sediments on top __________ the sediments at the

bottom.

g) We call the molten rock __________.

h) We call rocks that absorb water __________.

i) Unlike sedimentary rocks, igneous rocks do not contain any __________.

j) Detrital sedimentary rocks derive from the __________ of pre-existing

rocks.

k) The size of the crystals depends on how __________ the molten magma

solidified.

l) It may take __________ for sedimentary rocks to form.

3) The rocks riddle. You have to choose one rock and write two

characteristics of your rock. Your classmate have to guess the

name of the rock. For example:

ROCK CHARACTERISTIC

Marble - It's a metamorphic rock - It derives from limestone.

SOURCES:

- Sparkleboks: http://www.sparklebox2.co.uk/

- Sedimentary Rocks, by Pamela J. W. Gore, Georgia Perimeter College:

http://facstaff.gpc.edu/~pgore/geology/geo101/sedrx.htm#Terrig

- BBC KSbitesi!e:

http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/rock_cycle_9.

shtml

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