Temperature and Volcanism• Magma coming out of volcanoes.• Experiences of people engaged in mining activities.
How do we know about Earth’s interior?• Through INDIRECT EVIDENCE, mostly from seismic waves caused by earthquakes.• As we have no technology to go inside the earth ,indirect evidence is the only option for scientists to develop a theory.
Seismic waves : What are they?• Seismic waves are waves of energy that travel through the earth, and are a result of an earthquake, explosion, or a volcano that imparts low-frequency acoustic energy.
Seismic waves• P waves - Primary waves• S waves - Secondary waves• L waves – Lateral waves
As Seismic waves behave like light waves..• They refract and reflect • We record this on the at different boundaries surface and observe the and zones and move at changes and thus different speeds in the interpret them. Lets same period of time. have a look how?
The Four • The Earth is composed ofLayers four different layers. The crust is the layer that you live on, and it is the most Crust widely studied and Mantle understood. The mantle is much hotter and has the Outer Core ability to flow. The outer core and inner core are even hotter with pressures Inner Core so great you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth!
Crust• The crust, the outermost layer, is rigid and very thin• Oceanic Crust (beneath the ocean) is about 5 km thick• Continental Crust (under land) averages about 30 km and 100 km deep.• Like the shell of a hardboiled egg
Mantle• The Mantle is a dense, hot layer of semi-solid rock approximately 2,900 km thick.• The mantle contains more iron, magnesium, and calcium than the crust• is hotter and denser because temperature and pressure inside the Earth increase with depth.• As a comparison, the mantle might be thought of as the white of a boiled egg.
Core• the core, is nearly twice as dense as the mantle because its composition is metallic (iron-nickel alloy).• the Earths core is made up of two distinct parts: – a 2,200 km-thick liquid outer core – a 1,250 km-thick solid inner core – As the Earth rotates, the liquid outer core spins, creating the Earths magnetic field.
The core is important as..• It is thought to be the main reason behind the driving forces of convective currents in Mantle.• It is responsible to maintain Earth’s magnetic field.
If the core stops spinning, the magnetic field will collapse resulting indestruction of Earth’s surface by violent solar storms.