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Grade 7 Social Science August Cycle Test
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- 1The Richter scale is a scientific way of measuring the strength of earthquakes that was developed in 1935 by US geologist Charles F. Richter.A minor quake that rates less than 2.0 on the Richter scale is known as a micro earthquake and isn't generally strong enough to worry people. A major quake will reach something like 8.0 on the Richter scale and is likely to cause widespread damage and casualties.
- 2Scientists who study earthquakes are calledseismologists.
- 3structure of the earthearth's structure is made of 3 layers
crust
mantle
core - 4Crustsolid outer part of earth
- 5mantlearea of hot molten - heated to a very high temperature so it becomes liquid - rock beneath the earth's crust
- 6corecore of the earth - at the centre of the earth - inner core and outer core
- 7earths crust divided intooceanic crust - oceans floors made up of oceanic crust
thinner
usually less than 10km thick
heavier rocks rich in magnesium and iron
generally a younger crust because of volcanoes continually erupting on the ocean floor - 8earth's crust divided intocontinental crust
makes up the continents
thicker than oceanic crust
usually 30km thick
made of rocks rich in silica e.g. granite
40% of earth's surface - 9look at peach as model for earths structurepip = core
flesh = mantle
skin = crust - 10what part of the earth's structure is under the oceans?oceanic crust
- 11what parts of the earth are solid?oceanic crust and continental crust
- 12how the crust movesearth's crust is divided into large slabs called tectonic plates
these float on the liquid mantle underneath the earth's crust
some are ocean, some are land and some are both - 13plate marginsedges of tectonic plates
- 14convection currentscircular movements of material in the mantle
- 15tectonic plates move really slowly along the edges - these ages are called plate margins/boundariestectonic plates move at around 3cm a year
- 16how convection currents in the mantle cause tectonic plates to moveheat from the earth's core creates convection currents in the mantle
close to the earths surface the liquid mantle cools down
the cooler material sinks back into lower parts of the mantle
circular movement in the mantle works like a current that moves the plates that float on top of the mantle - 17the moving plates create and destroy the earth's crustnew crust is made a liquid rock bubbles up from the mantle when a volcano erupts - the hot lava from the volcano cools down to form solid rock
- 18in other places parts of the crust are destroyedwhen tectonic plate slides under another tectonic plate then the crust melts and is drawn into the liquid mantle
- 19earth creates new crust and destroys old crustthats why earth has stayed about the same size for billions of years
- 20name one plate that is mostly land and one that is mostly oceanland = Eurasian plate
ocean = Pacific plate - 21what tectonic plate is South Africa on?African plate
- 22name one plate that is North, South, East and West of the African plateN = Eurasian plate
S = Antarctica plate
E = Indian plate
W = South American plate - 23volcanoopening in Earth's crust through which lava and ash erupt
- 24lavamolten rock that cools on Earth's surface
- 25name a volcano situated in the ring of fireMount St Helens explosive volcano west coast of America
- 26world's most active volcanoes occur around the edge of the Pacific Plate calledThe ring of fire
- 27Active volcanoesvolcanoes that are erupting or that are expected to erupt in the near future
- 28do volcanoes create or destroy new crust?create new crust
- 29what is the nearest volcanic area to South Africanear Madagascar
- 30Why volcanoes occurabout 1500 active volcanoes = volcanoes known to have erupted
occur in areas close to plate margins
when earth's crust moves it disturbs the mantle and the crust which results in a volcano or earthquake - 31Some volcanoes occur when plates move apartas the plates move apart, openings expose areas of the mantle allowing hot lava to erupt
- 32volcanoes can also be caused by colliding tectonic plateswhen plate slides under another plate - the one underneath begins to melt back into the mantle - some of the melting plate works its way through the earths crust and erupts as a volcano
- 33write two sentences that explain why volcanoes occur at places where plates move together use mantle, erupt, meltingwhen the earth's crust moves, it disturbs the mantle and the crust which results in a volcano or earthquake
when a tectonic plate slides under another plate, it begins to melt back into the mantle
some of the melting plate works its way through the crust and erupts as a volcano - 34—Name the missing plates at A,B & C
- 35name two plates that are moving away from each otherAfrican and South American plates
Eurasian and North American plates - 36Effects of earthquakescause the foreign to shake violently
buildings collapse and people are crushed
earthquakes under the sea can cause Tsunamis which wash over land killing people and destroying buildings
broken gas pipes and petrol pumps can cause fires after an earth quake
people can be left homeless
polluted water and decaying bodies cause disease to spread easily - 37tsunamilarge wave of water caused by an earthquake in the earths crust
- 38some communities at higher risk than othersurban areas more at risk than rural - large numbers of people/buildings
people who live close to the sea where earthquakes occur may experience tsunamis
places where buildings are poorly made
communicates with poor rescue plans
areas without good communication links are in danger of not being able to phone for help - 39Developing countries like Haiti and Mexico suffer badly when earthquakes strikegovernments do not have enough money to deal with effects of a large earthquake
they rely on help from other countries
they don't have access to experienced medical teams/supplies
their building are not as strong as those in developed countries - 40earthquakes developing countries suffer badly when earthquakes strikeusually poor
governments don't have funds to deal with effects of earthquakes
rely on help from other countries
developed countries are richer
governments build stronger buildings
have rescue teams and doctors - 41name two areas in the world where you would not want to live if you want to avoid the risk of earthquakesCalifornia
Islands in the Pacific Rim - ring of Fire - 42one year after the quake in Haiti1,8 million people had received help
500 000 people got temporary homes
720 000 were given clean water
800 000 had access to safe toilets
39 schools were up and running
13000 teachers were trained
nearly 1 million books given to schools - 43reducing the risk of earthquakesbuild stronger better buildings
have good rescue plans and well trained rescue teams
doctos, supplies and emergency food and water
have good communication systems
electricity and gas cut off as earthquake strikes - 44suggest three ways in which damage from an earthquake could have been reducedbuildings approved by engineers and strict building regulations
earthquakes happen suddenly and without much warning - have seismometers to chart the movement of the earth
have basic first aid training - 45You might think Earth is a giant lump of rock, but you'd be wrong—it's more like a freshly boiled egg: there's a hot, molten core bubbling away inside a surprisingly thin outer crust.The countries we live in feel like they're safely anchored on solid rocky foundations, but really they're fixed to enormous rocky slabs called tectonic plates that can slide around on the molten rock beneath. Imagine living your life on an eggshell!
- 46ways to lessen damage caused by earthquakeshave disaster supplies on hand
have a clear communication plan
identify safe places inside and outside
check for hazards in the home
help your community put plans in place - 47name the tectonic plates that meet near HaitiCaribbean Plate and the North America Plate
- 48Earthquakes happen at places called faults (or fault lines) where the jagged edges of two tectonic plates grind against one another. Most earthquake activity happens in the middles of the oceans where plates are pushing apart on the floor of the sea.Some of the most violent earthquakes happen around the edges of a huge tectonic plate in the Pacific Ocean, forming an intense area of activity known as the Ring of Fire (so-called because there are many active volcanoes there too).
- 49Tectonic plates are constantly moving—in incredibly slow motion—and we don't even notice most of the time. But every once in a while two grinding plates will suddenly jolt into a new positionThe energy released by this movement creates an earthquake. It starts at a point inside Earth called the focus where the moving plates are in contact, then travels through the ground as very low-frequency sounds called shock waves or seismic waves. The greatest damage happens at a place called the epicenter, which is the point on Earth's surface above the focus. Earthquakes continue until all the energy released at the focus has been safely dissipated. Even then, there's still a chance that further earthquakes, known as aftershocks, will happen for some hours or even days afterward.
- 50Haiti 12 January 2010 close to capital - Port-au-Prince strongest quake in 250 years Caribbean plate4000 schools damaged/destroyed
600 000 had to leave their homes
most of Haiti's communication destroyed
so help was slow in arriving
if international aid had arrived earlier many more lives could have been saved
cholera broke out killing 900 and infecting 216 000
19 million cubic metres of rubble - 51Haiti one of worlds poorest countries 2 million people live in port-au-prince before the quake 86% of people lived in poorly built concrete buildings2010 - more than 70% lived on less than R10 per day
- 52Give 2 examples of poverty in HaitiHaiti does not produce enough food to feed its people and animals and has to import 60% of the food it needs
low educational levels mean Haitians can't move out of poverty - 53how does being poor make the impact of earthquakes worsenatural disasters have crippled the economy
105 000 homes were destroyed - these are poorly built because the people are so terribly poor
most of Haiti's agriculture was destroyed in the earthquake leaving them economically completely devastated, and resulting in no food being available for survivors and no plan being in place to help the victims - 54Haiti statistics3.5 million people affected by quake
230 000 people died
300 000 were injured
over 105 000 homes were destroyed
1,5 million people were made homeless - 55choleraa serious disease carried in water that causes diarrhoea and vomiting and may result in death
- 56Explain why earthquakes occur close to plate marginsAt plate boundaries the plates are sliding past one another or one plate is also diving beneath the other.
These plates lock for a period of time causing stress to build up. When they unlock and lurch forward this causes a quake. - 57match letters on diagram with labels oceanic crust mantle convection currents continental crustA) mantle
B) oceanic crust
C) continental crust
D) convection currents
- 58what causes convection currents in the mantlethe earths mantle has convection currents because the core's heat energy is transferred to the mantle causing it to rise towards the earth's surface which is cooler
- 59how do convection currents cause plates to movethe earth's crust is divided up into pieces called plates - heat rising and falling inside the mantle creates convection currents (heat radiates from the core) - the convection currents move the plates
- 60Name one part of the Earth other than the crust that is solidthe inner core is solid
- 61in which part of Earth's structure is most new rock createdthe oceanic crust
- 62in which region of earth does the rock granite occurcontinental crust
- 63label the names of the missing tectonic plates at A, B & CA=African plate
B=Pacific plate
C=South American plate
- 64Which twplates are moving apart and which two are moving togetherAfrican and South American are moving apart
Nazca and South American are moving together
- 65—make sure you know where Haiti is on the map
make sure you know where lots of earthquakes occur
- 66—
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- Flashcards on Grade 7 Social Science August Cycle Test, created by mantha on 17/08/2015.
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