Earth is the third planet from the Sun and the only object in the Universe known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4 billion years ago.[24][25][26] Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.[n 5] Earth's axis of rotation is tilted, producing seasonal variations on the planet's surface.[27] The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earth's orientation on its axis, and gradually slows its rotation.[28] Earth is the densest planet in the Solar System and the largest of the four terrestrial planets. Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earth's surface is covered with water, mostly by oceans.[29] The remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates the Earth's magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earth's history, life appeared in the oceans and began to affect the Earth's atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms. Some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earth's distance from the Sun, physical properties, and geological history have allowed life to evolve and thrive.[30][31] In the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species[32] that ever lived on Earth are extinct.[33][34] Estimates of the number of species on Earth today vary widely;[35][36][37] most species have not been described.[38] Over 7.4 billion humans live on Earth and depend on its biosphere and natural resources for their survival. Humans have developed diverse societies and cultures; politically, the world has about 200 sovereign states.

1. Our changing earth

3. •A tectonic plate (also called lithospheric plate) is
a massive, irregularly shaped slab of solid rock,
generally composed of both continental and
oceanic lithosphere. Plate size can vary greatly,
from a few hundred to thousands of kilometers
across; the Pacific and Antarctic Plates are
among the largest. Plate thickness also varies
greatly, ranging from less than 15 km for young
oceanic lithosphere to about 200 km or more for
ancient continental lithosphere (for example, the
interior parts of North and South America).

6. •An earthquake (also known as a quake, tremor
or temblor) is the perceptible shaking of the
surface of the Earth, resulting from the sudden
release of energy in the Earth's crust that creates
seismic waves. Earthquakes can be violent
enough to toss people around and destroy
whole cities. The seismicity or seismic activity of
an area refers to the frequency, type and size of
earthquakes experienced over a period of time.

7. •The rocks Larry that make up the Earth’s crust
are pushed and pulled in different directions.
•Sometimes, the rocks aren’t strong enough and
break causing the Earth to shake — an
earthquake.
•This is like if you bend a stick, it will bend so far
then snap all of a sudden. The line where the
Earth's crust snaps is called a fault.

9. •Faults are shown on geological maps
Manuel using a thick black line like on this
map.

10. •Earthquakes can cause a lot of damage to
buildings. This picture shows the result of an
earthquake in Turkey.

12. •The OneGeology map shows Mount
Etna in Sicily, Italy. It is marked with
an X. The orange colour on the map
indicates the rocks and lava from
the volcano.

14. •Can you see the black fault lines on
this map of the San Andreas Fault in
California? Faults are long breaks in
the rocks that make up the Earth's
crust.

15. •When an earthquake occurs, it creates
shockwaves which are a bit like the vibrations
you feel if you hit a drum. These shockwaves
travel through the earth and can be measured
using a seismometer and are recorded on a
seismograph. Click on the globe picture to learn
about the 3 different types of shockwave and
how they travel through the earth.

16. Earthquakes cause shockwaves
•Shockwaves travel through the
Earth in different ways and can be
measured by scientists to work out
the size and location of the
earthquake.

23. What is a volcano?
• A volcano is a mountain that opens downward to a pool of
molten rock below the surface of the earth. When pressure
builds up, eruptions occur. Gases and rock shoot up through
the opening and spill over or fill the air with lava fragments.
Eruptions can cause lateral blasts, lava flows, hot ash flows,
mudslides, avalanches, falling ash and floods. Volcano
eruptions have been known to knock down entire forests. An
erupting volcano can trigger tsunamis, flash floods,
earthquakes, mudflows and rockfalls

24. •A volcano is formed when hot molten
rock, ash and gases escape from an
opening in the Earth’s surface. The
molten rock and ash solidify as they
cool, forming the distinctive volcano
shape shown here.

27. •The OneGeology map shows Mount
Etna in Sicily, Italy. It is marked with
an X. The orange colour on the map
indicates the rocks and lava from
the volcano.

28. Volcanoes can produce different types of lava.
Some is runny and flows down slope; it has a
smooth, ropey, wrinkled texture. This is called
Pahoehoe lava.
Some volcanoes can be more explosive and
produce hot gasses and much thicker rough
textured lava that is sticky. This is called Aa
lava.

30. •Lava that erupts under water is
called Pillow Lava because it
forms shapes like pillows. They
wouldn’t be very comfy to sleep
on though!

31. •The Earth’s surface is made up of several
tectonic plates which are constantly moving,
although very very slowly. Where tectonic plates
are being pushed together, some of the Earth’s
crust is pushed deeper into the Earth’s mantle
where it melts and rises to the surface again to
form volcanoes. A large area where this occurs
on earth is called the Pacific Ring of Fire and is
shown on these globes.

33. •Where tectonic plates are being pushed
apart, openings in the Earth’s crust
allows molten rock to escape, forming
volcanoes. An area where this occurs on
earth is called the Mid-Atlantic Ridge
and is shown on this globe.

34. •Volcanoes can also form in areas where
there is a hotspot in the mantle. This is
an extra hot plume of molten rock which
causes the earth’s crust to thin allowing
molten rock to escape onto the surface.
The movement of the earth’s tectonic
plates means that volcanoes form a trail
along the earth’s surface. An example of
this is Hawaii as you can see in this map.

36. How are volcanoes formed?
•Volcanoes are formed when magma
from within the Earth's upper mantle
works its way to the surface. At the
surface, it erupts to form lava flows and
ash deposits. Over time as the volcano
continues to erupt, it will get bigger and
bigger.

37. What are the different stages of volcanoes?
•Scientists have categorized volcanoes into three main
categories: active, dormant, and extinct. An active
volcano is one which has recently erupted and there is a
possibility that it may erupt soon. A dormant volcano is
one which has not erupted in a long time but there is a
possibility it can erupt in the future. An extinct volcano is
one which has erupted thousands of years ago and
there’s no possibility of eruption.

38. Why do volcanoes erupt?
• The Earth's crust is made up of huge slabs called plates, which fit
together like a jigsaw puzzle. These plates sometimes move. The
friction causes earthquakes and volcanic eruptions near the edges of
the plates. The theory that explains this process is called plate
tectonics.

39. What are plate tectonics?
•The theory of plate tectonics is a interesting story of
continents drifting from place to place breaking apart,
colliding, and grinding against each other. The plate
tectonic theory is supported by a wide range of
evidence that considers the earth's crust and upper
mantle to be composed of several large, thin, relatively
rigid plates that move relative to one another. The
plates are all moving in different directions and at
different speeds. Sometimes the plates crash together,
pull apart or sideswipe each other. When this happens,
it commonly results in earthquakes.

40. How many volcanoes are there?
• There are more than 1500 active volcanoes on the Earth. We
currently know of 80 or more which are under the oceans. Active
volcanoes in the U.S. are found mainly in Hawaii, Alaska, California,
Oregon and Washington.

41. What are the different types of
volcanoes?
•Volcanoes are grouped into
four types: cinder cones,
composite volcanoes, shield
volcanoes and lava
volcanoes.

43. What is the difference between lava
and magma?
• Magma is liquid rock inside a volcano. Lava is liquid
rock (magma) that flows out of a volcano. Fresh lava
glows red hot to white hot as it flows.

44. Why does lava take a long time to cool down?
•Lava cools slowly because lava is a poor
conductor of heat. Lava flows slow down
and thicken as they harden.

45. What is a pyroclastic flow?
• A pyroclastic flow is a fluidized mixture of solid to semi-solid
fragments and hot, expanding gases that flows down the sides of a
volcano. These awesome features are heavier-than-air emulsions that
move much like a snow avalanche, except that they are fiercely hot,
contain toxic gases, and move at phenomenal, hurricane-force
speeds. They are the most deadly of all volcanic phenomena.

46. What is lahar?
• A lahar is a type of mudflow or debris flow composed of pyroclastic
material, rocky debris, and water. The material flows down from a
volcano, typically along a river valley. It is very dangerous because it's
consistency and the way it acts is very much like cement. It is liquid
when it's moving, but when it stops, it solidifies. This can cause just as
much devastation as lava itself.

47. What is pumice?
• Pumice is a light, porous volcanic rock that forms during explosive
eruptions. It resembles a sponge because it consists of a network of
gas bubbles frozen amidst fragile volcanic glass and minerals. All types
of magma (basalt, andesite, dacite, and rhyolite) will form pumice

48. What is the largest active volcano?
• The world's largest, active volcano is Mauna Loa in Hawaii, where
famous coffee is grown in the rich volcanic soils. Mauna Loa is 13,677
feet above sea level. From its base below sea level to its summit,
Mauna Loa is taller than Mount Everest.

49. What is the Ring of Fire?
•The Pacific Ring of Fire is an area of frequent
earthquakes and volcanic eruptions encircling the
basin of the Pacific Ocean. The Ring of Fire has 452
volcanoes and is home to over 50% of the world's
active and dormant volcanoes. Ninety percent of the
world's earthquakes and 81% of the world's largest
earthquakes occur along the Ring of Fire.

51. When did Mount St. Helens erupt?
• On May 18, 1980, Mount St. Helens erupted. It's located in
southwestern Washington State in the Cascade Range. The blast was
heard as far away as Montana, Idaho, Canada and California. Fifty-
seven people died and the eruption caused $1.2 billion in damage.

53. WORK OF THE RIVER
• As rivers flow from highland to lowland they perform three
important jobs, they erode, they transport the material that
they have eroded and then they deposit it. small rivers flow
down steep slopes and erode river beds vertically
downwards. Larger rivers flow down gentle slopes and erode
banks laterally. Larger rivers reaching the end of their
journey flow over flat plains and deposit the material that
they had eroded upstream.

55. • The coastline as we know it is itself a feature caused by the erosion of
waves and the deposits they carry. Rocky cliffs may form where the
water meets the land as the waves scour parts of the coastline away,
leaving a vertical face above water and a platform below the sea. It
does this by cutting a notch out of the land near the bottom of the
cliff, which leads to instability above the notch. The land above the
notch is eroded away in a process known as mass wasting, while the
land below the notch is left intact to create a platform. If tectonic
action lifts the Earth's crust where the sea terrace is located, the
terrace may emerge above the water level to form a marine terrace.
Cliffs and Terraces

56. Sea Caves
• Sea caves are created by waves battering the
coastline. The waves throw particles of rock at the
land, which causes abrasion --- the process by which
land is slowly rubbed away by friction between the
coastline sediment and the headland rock. At weak
points in the cliffs along a coastline, the abrasion
rounds out a bowl-shaped feature at the bottom of
the cliffs called a sea cave.

57. Sea Arches
• Sea arches are the next step along from sea caves that
continue to be eroded by the waves. The feature is created
when two sea caves on each side of a headland join in the
middle, creating a tunnel through the cliffs. As this tunnel is
eroded and enlarged, the headland begins to take on the
shape of an arch, with a pillar of rock remaining in the sea
and a slice of land connecting it at its uppermost point to the
new headland, which has retreated from its original position.

58. Sea Stacks and Stumps
•As sea arches age, they become sea stacks.
These are features of coastal erosion that occur
when the land that connects the pillar in the sea
to the headland collapses, leaving a tower of
rock in the ocean. These stacks themselves are
eroded by the waves and become smaller, at
which point they are described as sea stumps.

59. glaciers

60. •A glacier begins when snow doesn't
completely melt away during the
summer. Each winter new snow falls
on top of the old snow. Thick layers
of snow are gradually compressed into
glacial ice.
Glacial ice

61. •Glaciers are made up of more than just ice
and snow. They contain water, rocks and
sediments. This can make the ice look very
dirty.
Glacial sediment

62. •A glacier might look like a solid block
of ice, but it is actually moving very
slowly. The glacier moves because
pressure from the weight of the
overlying ice causes it to deform and
flow. Meltwater at the bottom of
the glacier helps it to glide over the
landscape.

63. •Ice shelves form when glaciers
reach the sea and begin to float.
The Ross Ice Shelf in Antarctica is
a famous ice shelf.

64. •Chunks of ice can break off
an ice shelf or a glacier
that reaches the sea. This
is called calving. The ice
chucks form icebergs up to
250 km long and 100 km
wide. Very small icebergs

65. TYPES
•There are different types of
glaciers:
•Gordon glacierAlpine glaciers, which
begin high up in the mountains in
bowl-shaped hollows called cirques.
•Gordon glacierContinental glaciers,
which are continuous masses of ice

67. •When a glacier melts, all of
the rock, sand and mud that
it was carrying gets left
behind. Geologists call this
mixture of sediment till.

68. •There are alpine glaciers high up in
the mountains all over the world.
Some mountain ranges have enough
ice to form extensive ice fields. There
are ice caps in Iceland and huge ice
sheets in Greenland and Antarctica.

69. •Piles and ridges of
sediment deposited at
the edges and front of
glaciers are called
moraines.

70. •Meltwater carries rock Larry,
gravel, sand and mud away from
the glacier. The debris is
transported and deposited by
rivers Gordon and in lakes.

71. •Strong winds can blow fine sand
and silt hundreds of kilometres
from the front of the glacier.
This sediment, called loess, can
build up into thick layers. In
central China people have built
homes in loess.

73. •An active agent of erosion and
deposition in the deserts is wind. When
the wind blows, it lifts and transports
sand from one place to another. When it
stops blowing the sand falls and gets
deposited in low hill – like structures.
These are called sand dunes.