1.1 Structure of the Earth

Label the layers of the Earth.

What is the composition of the oceanic crust?

What is the age of the oceanic crust?

A rheid is a [blank_start]solid material that flows[blank_end].

The density of the continental crust is 2.7 g/cm3.

The average thickness of the oceanic crust is [blank_start]7km[blank_end].

The average thickness of the continental crust is [blank_start]35km[blank_end].

Partial melting is where a proportion of the [blank_start]minerals[blank_end] in a rock have a lower [blank_start]melting point[blank_end] allowing them to melt whilst the rest remain solid.

What minerals are peridotite composed of?

Peridotite is an ultramafic igneous rock with a [blank_start]coarse[blank_end] crystal grain size.

Properties of the [blank_start]lithosphere[blank_end]: - It is made up of the crust and top part of the upper [blank_start]mantle[blank_end]. - High geothermal gradient - It is [blank_start]solid[blank_end]. - It is made of igneous, metamorphic and sedimentary rocks. - P and S waves gradually [blank_start]speed up[blank_end] with depth. - Density 2.7 to [blank_start]3.3[blank_end] g/cm3.

Properties of the asthenosphere: - It is a [blank_start]rheid[blank_end] - It is 5% partially molten - low geothermal gradient - below the [blank_start]lithosphere[blank_end] - made of [blank_start]peridotite[blank_end] - P and S waves slow down - density [blank_start]>3.3[blank_end] g/cm3

At what depth is the Lehmann Discontinuity?

At what depth is Gutenberg discontinuity?

What depth is the lower mantle?

What is the depth of the inner core?

What is the depth of the upper mantle?

Direct evidence for the composition of the crust: B[blank_start]oreholes[blank_end] - [blank_start]Cores[blank_end] of igneous and metamorphic rock are brought to the surface from depths of about [blank_start]11[blank_end] km (geological) M[blank_start]ining[blank_end] _ Rocks can be observed at depth in [blank_start]mines[blank_end]. The deepest mine is about 4 km. V[blank_start]olcanic eruptions[blank_end] - Crustal rocks brought up in [blank_start]eruptions[blank_end] such as fragments from volcanic vent or magma chamber O[blank_start]phiolites[blank_end] - Oceanic crust is [blank_start]obducted[blank_end] and exposed by erosion allowing rocks such as [blank_start]basalt[blank_end], dolerite or gabbro to be seen

Direct evidence for the composition of the mantle: Mantle xenoliths - Peridotite is brought to the [blank_start]surface[blank_end] in volcanic eruptions. Ophiolites - Peridotite is sometimes found at the [blank_start]base[blank_end] of ophiolites. [blank_start]Kimberlite[blank_end] pipes - Bring up [blank_start]xenoliths[blank_end] of [blank_start]peridotite[blank_end] from the mantle from up to 250 km depth.

How are seismic waves used as indirect evidence for the state of the layers of the Earth? Asthenosphere: - [blank_start]Decrease[blank_end] in velocities of P and S waves due to reduction in [blank_start]rigidity[blank_end] caused by 5% partial melting. Lower Mantle: - Increase in velocity of P and S waves as pressure increases and rocks become more [blank_start]incompressible[blank_end]. Outer core: - P waves suddenly [blank_start]slow[blank_end] as they enter [blank_start]liquid[blank_end] outer core as rigidity is [blank_start]low[blank_end]. - S waves stop completely as they cannot be transmitted in a [blank_start]liquid[blank_end]. Inner Core: - P waves speed up at Lehmann Discontinuity as they enter [blank_start]solid[blank_end] inner core. - S waves are [blank_start]regenerated[blank_end] by P waves.

Indirect evidence for the composition of the Earth: [blank_start]Core[blank_end] - [blank_start]Iron[blank_end] meteorites - Earth has a magnetic field - Earth has a high average density of [blank_start]5.5[blank_end]gm/cm3 and the density of the oceanic crust is 2.9g/cm3 and the continental crust is 2.7g/cm3 so therefore the density of the core must be high. Mantle - [blank_start]Stony[blank_end] meteorites which are [blank_start]less[blank_end] dense like the mantle.

Complete the table to show each layer of the Earth with its approximate composition.