Flashcards
Geography
Cards in this deck (33)
- 1The Crustsolid outer layer
5-70km
forms land and rock under ocean - 2The mantlevery hot rock
80% of earth's volume
between crust and core
made of soft rocks/ molten magma - 3The coreInner = solid
Outer= hot molten material
radius= 8000km
avg temp 5000 degrees - 4Geomorphologystudy of earths physical features and processes that formed them
- 5igneous rocks"fire"
1st to form after earth cooled down 4 billion years ago
when magma ( liquid rock inside earth ) cools and becomes solid
Extrusive: form from hot material on surface.
volcanic and fissure eruptions
small, fine crystals, usually dark- Basalt
intrusive: from magma cooled inside earth's crust
large crystals that can be seen ( lighter colour) - Granite - 6sedimentarymost rocks on earths surface
form from sediments deposited in layers, usually on floor of lake or ocean.
sediments -> pieces of rocks, stones, remains of plants and animals, sand and mud that are worn off land and carried along rivers to oceans
sandstone, limestone, coal - 7metamorphicigneous and sedimentary rock changed by heat and pressure.
heat: rocks next to igneous intrusions below surface are "baked" by being close to molten rock.
contact metamorphism- elements in minerals in original rock recombine to form completely different minerals.
can happen deep underground or on surface when lava comes in contact with other rocks.
pressure: rocks squashed between moving land masses.
crystals in rocks flattened or stretched by pressure. - 8random paragraphwhen volcanoes erupt molten rock appears on earths surface, forming new igneous rock. liquid rock that flows on earths surface is lava. this kind of igneous rock is extrusive rock. liquid rock inside earth is magma. magma cools inside crust, turns into intrusive igneous rock such as granite. rocks that cool deep below earths surface have large crystals.
- 9The rock cyclecycle of processes that causes rocks to form, break down, change and reform over geological time.
magma rises into earths crust.
igneous- weathered and eroded. sediments are formed. sediments pressed and cemented together to form sedimentary rocks.
sedimentary- undergo tremendous heat and pressure and form metamorphic rocks.
metamorphic- melted due to tremendous heat in mantle. melted rock forms magma which cools and hardens to form igneous. - 10intrusive igneous activity and other featuresmagma less dense than solid rock- joints and cracks in crust. when it cools, forms igneous intrusions.
classified by: shape
size
depth
relationship with surrounding rock
see on surface after weathering and erosion remove rocks above intrusions. - 11Batholiths- largest and deepest
- some cover thousands of square kms and may be associated with continental movements.
- form deep in crust
- magma cools slowly to form rocks with large crystals. - 12Laccoliths- much smaller than batholiths
- dome shaped intrusion
- forms when magma forced between layer of sedimentary rock and pushes up the layer of rock above it
- some cause mountains to be pushed up.
-effect on surrounding rock: toothpaste on newspaper - 13Monoliths- large intrusion: often stands above surrounding land as a towering wall of rock
- may be part of other igneous features : batholiths - 14dykes and sillsdyke: - magma forces its way vertically through layers of rocks
- only a few metres across
- dolerite= common
sill: - magma forces its way between rock strata and cools
- form parallel to layers of strata
- many kms - 15Pipes- central vents of old volcanoes
- magma solidified form carrot-shaped intrusions into surrounding rock.
- "volcanic pipes" surface : 2/3 km under
- Kimberlite
- bottom of pipe= dyke - 16rock crystalsparts of rocks made up of minerals that grow as magma cools
strata- horizontal layers of sedimentary rock. - 17Plate tectonicstheory 1960s- geological features connected to movements of earths crust.
- 18continental drift theory1915, German geologist, Alfred Wegener couldn't produce enough evidence to prove.
: continents change their position over time by slowly moving on top of mantle
- used to be one large landmass that slowly broke up, producing continents in positions we know today.
1- Pangea: 180 mill years ago
2- Laurasia ( North ) 175 mill
Gondwanaland ( South )
3- L and G pull apart , slowly forming present continents 150-65 mill
4- Present - 19Evidence- similar fossils on southern continents
- rock formations south america and west africa same age and compostition
- mountains north america same rocks and structure as britain and sandanavia.
- ice erosion and ice deposition over southern continents: would have had to be close to south pole.
- ridges in oceans: rocks close to ridges= younger= ocean floors spread from original ridges.
- magma cools= igneous rocks, iron minerals in magma record position of earths magnetic field "fossil compass"
= expect minerals in same age rocks point same direction but dont
= suggests position of rocks changed. - 20plate tectonicscrust divided into 7 giant pieces and 12 small plates
most made of some continental crust and some oceanic crust
forces within mantle cause plates to move
plate boundaries = most movement - 21plate boundariesDivergent-
<- ->
new crust created from erupting volcanoes
Convergent
-> <-
1 plate forced under another into mantle. plate melts causing earthquakes and volcanic eruptions.
Transform
plates grind past eachother
associated with earthquake activity
can have all 3 at different parts of their margins
passive parts show little movement. - 22mechanics of plate movemntconvection currents ( circular movements of gases/ liquids, caused by heating and cooling )
1: Convection currents form above areas of high temp. in mantle
2: ^ causes liquid mantle to move
3: This movement drags solid crust above mantle in direction of convection current
4: Plates move apart, magma rises from mantle and fills gap between two plates
= new ocean crust created, causing ocean floor to spread - 23crust destroyed1: Convection currents drag denser oceanic plate under lighter continental plate.
sinking of oceanic plate at convergent boundary= subduction
area= subduction zones
2: Oceanic plate enters mantle- bend and crack forming deep trenches.
3: Process of subduction creates volcanic and earthquake activity.
4: Earthquakes near trenches, volcanoes inland, on continental plate.
volcanoes triggered by melting of oceanic plate as descends into mantle .
trench- deep crack in ocean crust, formed by subduction under another plate
ridge- area where new ocean crust is formed from magma rising from mantle - 24divergent of 2 oceanic platesmain feature= mid ocean ridge ( ridge of volcanic mountains that form boundary between 2 DOP)
created by volcanoes erupting at a plate boundary - 25divergent involving contintal crustcontinental crust splits and separates , 2 continental plates form
new oceanic crust fills space between separating continental plates.
East African Rift Valley
Rifting- pieces of crust crack and slide from sides of mountains due to divergence of continental crust
1: convection currents within mantle allow plume of magma to push under continental crust, causing it to crack.
2: Further upward pressure and sideways pulling causes blocks of land tear from crust and slip downwards . volcanoes erupt above new plate boundary creating new crust.
3: land masses move apart and new crust fills gap between separating continental crust -> new ocean. - 26convergent between ocean plate and continental plateoceanic plate pushed under continental plate = mountain range
1: oceanic crust denser because of mineral composition, forced under
2: oceanic plate enters subduction zone - cracks and bends creating deep sea trench. further subduction produces earthquakes throughout subduction zone.
3: melting of oceanic plate = igneous activity; volcanoes erupt on continental plate - 27convergent of 2 continentalneither can subduct because of similar material = collision of crust causes high mountain range
1: cannot subduct- crust bends and cracks and pushed upwards or sideways
2: mountains build up where plates collide made of sediments from sea floor , broken crust and erupting lava
3: plates continue to converge- plateau forms behind mountain. - 28definitionsvolcanic arc: volcanoes that form in mountains where an oceanic plate subducts under continental plate
island arc: chain of volcanic islands form above subduction zone with 2 convergent oceanic plates. - 29landforms with transform-crust neither created nor destroyed
- slide/ grind past
- most under ocean
- enable plates move sideways and divergent, convergent
- causes earthquakes - 30volcanic and earthquake zonesareas that have recorded some form of tectonic activity in recent past.
50 earthquakes a day- minor- no damage
50 volcanoes a year
2000 active/potentially active - 31cinder conesteep cone shaped hill with bowl-shaped crater at summit.
made of small rock fragments- cinders
formed from lava that contains gas bubbles.
can be hundreds metres tall
erupts violently - 32shield volcanoespread over wide area
largest
formed from thin lava
basalt
lava erupt from different vents at once - 33compositealternating layers of ash and lava
quiet eruption
thick lava flows down side and hardens into rock. ash formed of lava and magma shattered during violent eruption. gasses build up = ^ pressure under solidified rock in vent. gases eventually explode- shatter solidified rock, forms ash eruption- settles on sides of cone.