Science Term 3 2024

Question 1

Crust

Answer 1

Where we live
Has an irregular thickness varying from 5km beneath the oceans
Consists of mainly lighter rocks
Basalt in the oceanic crust
Granite in the continental crust
Basalt is denser (oceanic)
Granite is thicker but less dense (continental)

Question 2

Mantle

Answer 2

Beneath the crust
2,900km deep
Contains silicate rocks
Rich in iron and magnesium
Upper Mantle
Ridged behaves elastically on short time scales
Lower Mantle
Solid but flows on geological timescales

Question 3

Outer Core

Answer 3

The outer core extends from 2,900 km to about 5,150 km beneath the Earth’s surface
It mainly consists of liquid iron andnickel
The motion within this layer generates the Earth’s magnetic field
The convection currents within this liquid layer create the Earth’s magnetosphere through a dynamo effect

Question 4

Inner Core

Answer 4

Extends from a depth of about 5,150 km to the Earth’s centre at about 6,371 km.
The inner core is solid due to the immensepressureat this depth
It’s composed primarily of iron, with minor amounts of nickel and other lighter elements.

Question 5

Lithosphere

Answer 5

The lithosphere, about 10 to 200 km thick
Includes the uppermost mantle and the crust
It’s rigid and breaks under stress, which is why it’s broken up intotectonic plates
The lithosphere varies in thickness, being thinner at oceanic ridges and thicker beneath older oceanic and continental regions.

Question 6

Asthenosphere

Answer 6

Beneath the lithosphere, from about 100 to 350 km
Asthenosphere is the part of the upper mantle that exhibits plastic (or ductile) behaviour
The tectonic plates slide around on top of this layer
It’s composed of similar material to the rest of the upper mantle – mainly peridotite, a rock rich in silicate minerals.

Question 7

Mesosphere

Answer 7

Below the asthenosphere and extending to about 2,900 km is the mesosphere or lower mantle
region of strong, rigid rocks that deform slowly under the intense heat and pressure
It’s composed of silicate minerals that change in structure with depth due to increasing pressure.

Question 8

Alfred Wegner

Answer 8

He was a scientist in the time 1900s
He died in 1930 when he was 50 yrs from freezing to death
His theory was that the continents were once all together
He spent his whole life trying to prove that

Question 9

Evidence to suggest continents were once conected

Answer 9

Evidence 1:
The apparent fit of the continents
The coasts lines fit together
Evidence 2:
Fossil Correlations
Life
Fossils of ancient creatures and where they were located
Mesosomas are only found in two places
Southern tip of south America and southern tip of south Africa
During the days that the mesosomas thrived the land was connected
At some point later on the land masses where ripped apart
When you put the land together the fossil places match up together
Evidence 3:
Rock and mountain correlation
Geologic structures
Same distribution as the fossil
When the continents split apart the rocks went with the land mass
Evidence 4:
Paleoclimate Data
Past climate
Glaciers
When the glaciers move, they leave evidence
They are in the amazon rainforest and the hot sticky jungles of Africa
Now-days they can’t be found here because it was too hot
Rocks
Cedementry rock
Bituminous coal is made of tropical plant remains
Now they are in colder areas
Which is impossible

Question 10

Harry Hess

Answer 10

Seafloor spreading
Ridges are located above zones of upwelling in the magma resulting in the creation of seafloor
He also proposed a subduction as the mechanism for recycling the seafloor
The magma is pushed up and slips underneath the tectonic plates
It then moves the plates apart and the magma hardens into new crust

Question 11

Magnetic Striping

Answer 11

The rocks on the floor have magnetic stripes parallel with underwater ridges
The magnetic field of the earth has changed many times with the north and south pole being flipped
The striped show this reversal and indicate that the youngest rock (the crust closed to the opening/tectonic plates) is closed to the ridges and the oldest closest to the trences

Question 12

Convection Currents

Answer 12

When the magma becomes less dense it rises
When the magma becomes denser it falls
It continues like this at all times
This means the Earth’s ‘underneath’ is always moving, then causing the tectonic plates to move

Question 13

Latitude and Longitude

Answer 13

Latitude = how far North or South of the Equator
Longitude = how far East or West of Prime meridian
Prime Meridian = is the line in the Earth going from the top (north) to the bottom (south)