Transcript Slide 1

22.3 EARTH’S MOON
THE MOON
•Diameter of the moon is
3,475 km, ~1/4 Earth’s
diameter of 45,756 km
•Moon’s density is 3.3 times
that of water, Earth’s density
is 5.5 times that of water
•Lower density is due to
small iron core
•Gravitational pull is 1/6 the
gravity on Earth (150lb = 25lb
on Moon)
THE LUNAR SURFACE
•Moon has no atmosphere or
tectonic forces
•Moon has no weathering,
erosion occurs when particles
bombard its surface
•Craters - depressions produced
by impact of debris or meteoroids
•Large craters about 250 km in
diameter
•Most of the ejected material
lands near crater
•Rays are splash marks
Highlands, Maria, Regolith
•Highlands – Densely pitted, light-colored areas, highest
peaks ~8 km
•Maria – Dark, relatively smooth areas
•Ancient beds of basaltic lava caused by asteroids puncturing
surface
Rilles
•Long channels similar
to valleys are called
rilles.
Highlands
Maria
Crater
•Regolith - layer of gray
debris, similar to soil,
over lunar surface
Formation of Moon’s Features
•Highlands: First original crust with many
craters (4.5 BYA)
•Maria basins: Next –
lava flows (3.2-3.8 BYA)
•Rayed craters: Last –
formed over highlands
and maria basis,
regolith (soil/dust)
sprays out upon impact
Highlands
Maria basins
Rayed craters
Formation of Moon
•About 3.5 billion years ago when
the Earth’s was still molten lava, a
body the size of Mars impacted
Earth
• Part of the object that hit the
Earth was absorbed by the Earth,
but the impact also ejecting huge
quantities of crust and mantle rock
•A portion of ejected material
entered an orbit around Earth,
combining to form the Moon
Summary Review
1. Describe
Highlands
2. Describe
Maria
3. Describe
Rayed
Craters
4. How did the
moon form?