Tectonic activity

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Tectonic activity
Tectonic activity

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Unit Contents

• 1.Continental drift
• 2. Plate tectonics 3. Volcanic activity
• 4. Earthquakes
• 5. Managing tectonic hazards

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Continental drift
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Activity 1

• List more pieces of evidence (proofs) which show
  that the plates of the Earths crust are moving?
• Which eras of the earth are shown in your
  handout? (write also the approximately time )

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Solutions

• Similarities of species ( FOSSILS)
• geological structures across oceans
• paleomagnetism
• ( young rocks at the mid-ocean ridges)
• Permian 260, Jurassic 180, Cretaceous 130,
  Tertiary 60

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Plate tectonics

• The structure of the earth
• The earth is made up of 4 distinct layers

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Characteristics of Continental crust

• is largely composed of granite and is sometimes
  referred to as sial due to the volume of silica
  and aluminium in its make up
• is less dense than the basaltic oceanic crust
  (also known as sima, because of the silica and
  magnesium in its make up)
• is considerably thicker than sima

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Rock types
Sedimentary rock sandstone
Metamorphic rock slate
Igneous rock
granite Igneous rocks are crystalline or glassy
rocks formed by the cooling and solidification
of molten magma. Igneous rocks comprise one of
the three principal classes of rocks, the others
being metamorphic and sedimentary.
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• .

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Activity 2

• Describe the 4 layers of the earth

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Solution

• 1. Inner core Solid iron inner core
  (5150-6370km)
• 2. Outer core Liquid iron outer core
  (2891-5150km)
• 3. Mantle May be divided into two subdivisions,
  the semi liquid upper and solid lower mantle
  (40-2891km)
• 4. Crust Solid, divided into two different
  types, continental and oceanic crust. Depth
  varies from (0-40km)

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Activity 3

• Label the structure of the earth in your copy

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(No Transcript)
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The earths crust

• Crust, the upper layer of the Earth, is not
  always the same. Crust under the oceans is only
  about 5 km thick while continental crust can be
  up to 65 km thick. Also, ocean crust is made of
  denser minerals than continental crust.
• The tectonic plates are made up of Earths crust
  and the upper part of
• the mantle layer underneath. Together the
  crust and uppermantle are called the lithosphere
  and they extend about 80 km deep.
• The asthenosphere is ductile and can be pushed
  and deformed like putty in response to the warmth
  of the Earth. The flowing asthenosphere carries
  the lithosphere of the Earth, including the
  continents, on its back.

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• Glossary
• 1 Continental drift
• Core
• The central part of the earth.
• Mantle
• The layer of the earth below the crust and above
  the core.
• Crust
• The outermost layer of the earth.
• Plates
• Large sections of the earth's crust.
• Continental drift
• A theory that the continents were all joined
  together 200 million years ago. They then split
  into the continents as we know them.
• Magma
• Molten rock below the earth's surface.
• Lithosphere
• The solid, rocky, outer layer of the Earth, made
  up of the crust and the solid part of the upper
  mantle.
• Asthenosphere
• The semi-liquid layer of the mantle below the
  lithosphere.

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2. Plate tectonics
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Activity 4

• What does the theorie of plate tectonics
• explain?
• Explain the movement of the plates.
• Study the diagram in your copy which shows some
  of the main plate boundaries of the world. Label
  the blank boxes of the plates. Add the Somali
  Sub-Plate.

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Activity 5

• Describe, draw and find an example to all four
  types of margin.

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The earths active belts
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Activity 6

• Search following volcanoes in your atlas and add
  the numbers in the map in your handout.
• Mount Wrangel Mount St. Helens Mount Rainier
  Popocatepetl Paricutin Fuego Irazu Mont Peleé La
  Soufrière Cotopaxi Nevado del Ruiz Sajama San
  Pedro SanJosé Surtsey Ätna Vesuv Asahi Fujiyama
  Kilimanjaro Kljutschewskaja Pinatubo Krakatau
  Tambora Merapi Mount Lamington Mauna Loa Kilauea

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• Glossary
• Plate margin
• The place where two plates meet. Also known as a
  plate boundary.
• Volcanic ridge
• A ridge of lava formed along a constructive
  plate margin.
• Volcanic island
• These are islands which have been formed from
  under the ocean by volcanic eruptions.
• Trench
• The deepest part of the ocean along a subduction
  zone.
• Subduction zone
• In this zone, one plate descends into the mantle
  moving under a less dense plate. This creates a
  deep trench.
• Continental crust
• The earth's crust above sea level which makes up
  the continents. It is typically around 40km in
  thickness.
• Oceanic crust
• The earth's crust below the ocean. It is much
  thinner than the continental crust being around
  6km in thickness.
• Continental shelf
• Continental crust bordering the continents
  covered by relatively shallow water.

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3. Volcanic activity

• 2 types of volcanic activity
• Intrusive (plutonic) and extrusive (vulcanic)
• Batholith, dikes, sills Vulvano, lava, lava
  plateau

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Extrusive volcanic activity

• Definition A volcano is an opening in the
  earth's crust through which magma, molten rock,
  and ash are erupted on to the land.
• Volcanoes tend to be conical in shape, although
  there are a variety of forms depending on .
• Most volcanoes are located at the edges of plate
  boundaries, although some are found in the
  interior of plates.

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Activity 7

• Describe, draw and give an example of the main
  types of volcano (handout)

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3.1 Geothermal Activity

• Geothermal activity is caused by the transfer of
  heat from depth to the earth's surface. Listed
  below are the surface manifestations of
  geothermal activity
• Warm ground, hot steaming grounds, hot pools, hot
  lakes, hot springs, fumaroles and solfatares,
  geysers, hydrothermal eruptions, exhalations

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3.2 Geothermal gradient

• The geothermal gradient is the natural increase
  in the temperature of the Earth as depth
  increases.
• Mean value 3/100m
• South Africa 1/130m-135m
• Zurzach 1/14m
• Ätna 1/5m

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Activity (Longman)

• Answer questions 2-7 on page 22-23 in Longmans
  Activities section. (Leave out question 4)