Earth Science not mine. PTPA

2. According to the solar nebular theory, planets are
formed through the process of accretion.
Process of accretion:
1.Accretion of centimeter-sized particles
2. Physical collision of kilometer-sized planetesimals
3. Gravitational accretion of planetesimals
4.Formation of molten protoplanet due to heat
of accretion

3. The final step is differentiation
of Earth. During differentiation,
heavy or dense materials like
nickel and iron sink to the
center of the Earth while light
materials rise to the surface.

4. LAYERSOFTHEEARTH(INSUMMARY)
Layer Position Composition
crust outermo
st
mostlylight elementssuchas
Si,O andAl
mantle middle rocks
core innermo
st
densemetalslikeNi andFe

6. • Outermost and thinnest layer
•The thickness of this layer depends on
its age. The thicker the layer, the older
the crust.
•Most common elements by weight
include: O (46.6%), Si (27.7%), Al (8.1%),
Fe (5%), Ca (3.6%), Na (2.8%), K (2.6%),
and Mg (2.1%).
• Has two types: continental and oceanic

7. Continental Oceanic
 Light-colored
 Granitic
 Less dense
 Thick layer
 40-70 km
 Coarse-textured
 Dark-colored
 Basaltic
 More dense
 Thin layer
 50 km

8. • Separates the crust from the mantle
• Noted by the Croatian seismologist
Andrija Mohorovicic on 1909
• 5 km to 10 km below the oceanfloor

9. • Largest part/layer of theEarth 2900 km
thick
• Made up of molten rocks called magma
which circulates in currents determined by
the cooling and sinking of heaviermaterials,
and the heating and rising of the lighter
materials.

10. • About 80%of the Earth’s massis
concentrated on themantle.
• ASTHENOSPHERE –layer that lies after the
lithosphere (100kmto 250 km).Itis believed
to play a critical role in the movement of
plates on surface of Earth, according to the
Theory of PlateTectonics.

11. UPPER MANTLE LOWER MANTLE
 Lithosphere
 Rigid/solid
 660 km
 Asthenosphere
 Soft/magma
 2240 km
 Exhibits“plasticity”
 Convection
currents

12. •Boundary between the
lower mantle and the outer
core

13. • Two layers:outer (liquid) and inner (solid)
• The pressure in the inner core is sogreat
that the iron-nickel alloy cannotmelt.
• Earth’s molten metallic core gave rise to the
magnetic field.
• LEHMANN DISCONTINUITY –boundary
between the outer core and the innercore

14. OUTER CORE INNER CORE
Celsius
 Cause of Earth’s
magnetic field
 Iron and nickel
 Magnetic
 Liquid
 2300 km
 4000 – 5000 degrees 
 Iron and nickel
 Magnetic
 Solid
 1250 km
6000degrees Celsius