3
The Geosphere
120
The Earth: origin and composition
33.
Find out the thickness of the different layers of the
Earth and order them from thickest to thinnest.
Crust: between 6 and 70 km thick
Upper mantle: up to 670 km deep; around 600 km thick
Lower mantle: up to 2900 km deep; around 2230 km thick
Outer core: up to 5120 km deep; around 2220 km thick
Inner core: up to 6370 km deep; around 1250 km thick
In order from the thickest to the thinnest: lower mantle-outer
core-inner core-upper mantle-crust
34.
Make a table to compare the characteristics of the
continental crust and the oceanic crust.
Characteristics
Continental Crust
Ocean Crust
The age of materials
that formed it
More than 1000
million years old
200 million years old
Thickness
Between 10 and 70km Between 6 and
10km
Rocks that formed it Granite, clay and slate Basaltic rock
Superficial reliefs that
composed it
Continental platform,
continent and islands
Sea floor
35.
Were all materials distributed according to their density
from the very beginning? Explain your answer.
No, the density differentiation happened after the process
called accretion of planetesimals.
36.
Explain why the following statements are true or
false.
a)
The seismic method only allows us to know the
composition of the Earth’s crust.
False, it allows us to
know the composition and the structure of the Earth’s
interior.
b)
The Earth is made up of solid materials.
False, it is
made up of solid materials and molten rocks like in the
upper mantle and in the outer core.
c)
The Earth’s crust has a uniform thickness of 50 km.
False, the thickness is variable in the Earth’s crust, for
example, the continental crust is thicker than the oceanic
crust.
d)
Denser materials in the geosphere are found on
the Earth’s surface.
False, in the geosphere the densest
materials are found in the inner core and the lightest ones
in the crust.
e)
The Earth’s mantle is located between the
Mohorovicic discontinuity and the Lehmann
discontinuity.
False because the Earth’s mantle is located
between the Mohorovicic discontinuity and the Gutenberg
discontinuity.
f)
The Earth’s inner core is solidbecause the temperature
is lower than in the outer core.
False, the inner core is
solid although its temperature is colder than in the outer
core, because the pressure is higher.
62
63
3. Thegeosphere
3
+
www
The Earth: origin and composition
33.
Find out the thicknesses of the different layers of
theEarthandorder them from thickest to thinnest.
34.
Make a table to compare the characteristics of the
continental crust and the oceanic crust.
35.
Were all materials distributed according to their
density from the very beginning? Explain your
answer.
36.
Explain why the following statements are true or
false.
a)
The seismic method only allows us to know the
composition of the Earth’s crust.
b)
The Earth is made up of solid materials.
c)
The Earth’s crust has a uniform thickness of 50 km.
d)
Denser materials in the geosphere are found on the
Earth’s surface.
e)
The Earth’s mantle is located between the Mohorovičić
discontinuity and the Lehmann discontinuity.
f)
TheEarth’s inner core is solidbecause the temperature is
lower than in the outer core.
37.
The following graph shows how seismic waves
move around the planet. Which seismic wave is
travelling at a higher speed? Which layers of the
Earth do they go through?
Minerals
38.
Whichpropertyofmaterials
does the image show?
The use of rocks
53.
Explain which rocks provide the following building
materials:
54.
Whyarecoalandpetroleumreferredtoasfossilfuels?
55.
What is sandpaper? Explain why it is not made of
fragments of gypsum or talc.
56.
Copy and complete the table in your notebook for
the following rocks: petroleum, chalk, limestone,
clay and coal.
57.
Research how concrete and bricks are made. Make
a diagram.
Extraction of minerals and rocks
58.
Complete the sentences in your notebook.
a)
The rocks extracted from ….. are cut into blocks.
b)
….. are horizontal tunnels in underground mines.
c)
….. is sediment that is usually extracted in or near large
riverbeds.
59.
Explain themeaningof the terms
deposit
and
mine
.
39.
Describe four properties of minerals.
40.
Explain if an ice cube and coral used in jewellery
are minerals or not.
41.
Investigate and then copy and complete the table
in your notebook.
42.
According to the Mohs scale, what is the hardness
of a mineral that scratches orthoclase but is
scratched by quartz?
43.
Explain how can you distinguish white quartz from
orthoclase which is the same colour?
44.
Find out why the colour and streak of a mineral
isn’t always the same.
45.
Findoutwhypyrite isalso referred toas ‘fool’sgold’.
Rocks
46.
Explain the three characteristics that are used to
classify rocks.
47.
Pumice is a rock that floats in water. Why do you
think this is? Is it a natural or an artificial rock?
Justify your answer.
48.
Copy the following terms in two columns in your
notebook and then match them.
A:
limestone, granite, clay, marble, basalt, chalk, detrital
sedimentary
B:
non-detrital sedimentary, plutonic, volcanic, foliated
metamorphic, non-foliated metamorphic
49.
Are there any rocks which are not composed of
minerals? What type of rocks are they?
50.
When1kgofgranitewasanalysed inthe laboratory
using different chemical processes they obtained
250gofawhitemineral,300gofanothermineral,
almost black, and the rest was a grey mineral.
a)
What is thenameofeachmineral thatcomposesgranite?
b)
Which mineral corresponds to the grams of minerals
above?
51.
On an excursion, Ana found a rock that contained
a plant fossil that lived on Earth millions of years
ago.What typeof rockdoyou think itwas?Explain
your answer.
52.
Which rock forms quartzite after metamorphism?
What size are the grains of the original rock?
60.
Find out what a
slag heap
is. What environmental
problems do they cause?
61.
Discuss this statement: ‘New generation mobile
telephones are made of stone’.
Speed of siesmic wave (km/s)
Depth (km)
0
Moho
Gutenberg Lehmann
Waves S
Mantle
Outer
core
Inner
core
Waves P
0
3
6
9
12
1000 2000 3000 4000 5000 6000
Rock
Use
Objects created with it
...
...
...
a)
glass
c)
cement
e)
brick
b)
concrete
d)
lime
f)
tile
STUDY SKILLS
❚
Create your own summary of the unit using
the
Key concepts
. Add any other important
information.
❚
Copy the following diagram in your
notebook and add the missing information
to create a conceptual map of the unit.
Slow but sure
In Chihuahua, Mexico, giant crystals were found in the
caveofNaica.Theyaremega-crystalsofselenite(avariety
of gypsum). For years, the Spanish investigator Juan
Manuel García has been studying how fast they grow.
Thanks to a special microscope designed by Japanese
engineers, we now know that these formations grow
at the equivalent of one hair every 100 years. However,
their growth has stopped in recent years due to mining
activities, to extract minerals from the underground
water that the minerals need to grow.
E
VA
VAN
DEN
B
ERG
National Geographic,
November 2011
(Translated and adapted)
a)
What is the text about?
b)
Can you explain the title?
c)
Why have the crystals stopped growing?
d)
Doyou think thegrowthof these formations canbe
observed by any person?
e)
Find out about selenite. Explain why water is
essential for its formation.
READ AND UNDERSTAND SCIENCE
You can record your
summary and listen
to it as many times
as you like to revise.
Mineral
Ore
Cassiterite
...
...
Lead
Hematite
...
...
Zinc
Chalcopyrite
...
❚
Createyourown scientificglossary.Define the following terms:
quarry,clast, sedimentarybasin,deposit,discontinuity,
reef,phytoplankton, fossil,gallery,gangue,geosphere,gravel,magma,metamorphism,mineral,ore, rock, sediment,
seismic wave
. Add any other terms you consider important.
The geosphere
layers
is divided in
is composed of
minerals
rocks
are classified by
are classified by
...
...
...
CONSOLIDATION
CONSOLIDATION
