Inside Planet Earth Page #10

but is extremely rare

elsewhere in the Earth's crust.

At these craters,

the levels of iridium

are 10,000 times higher

than normal.

Such high concentrations

have been found

in the sedimentary record

all over the world

at a consistent date

of 65 million years ago.

Recently, a crater

more than 110 miles wide

was detected off the coast

of Mexico's Yucatn Peninsula.

It, too, was created

65 million years ago.

It was formed

by a 10-mile-wide cosmic killer

which closed on Earth at

more than 60,000 miles an hour.

It struck with the violence

of the world's entire

nuclear arsenal

exploding 1,000 times over.

It sent out a ferocious fireball,

engulfing the land for

thousands of miles around.

Enormous fires raged for months,

destroying everything

in their path.

The impact may have had other

catastrophic effects as well.

The force was so great

that shock waves went out from

the point of impact in Mexico

around the world

and focused and concentrated

at the exact opposite point

of the Earth

in the Indian Ocean.

The exact opposite point

in those days

was the island of India.

And Rampino believes

the violent volcanic eruptions

which created the Deccan Traps

was triggered by the meteorite.

The effects of the impact

explosion and the volcanic flood

poured millions of tons

of dust and ash into the air,

plunging the world

into darkness.

Nitrogen, sulfur, and oxygen

in the atmosphere

combined to form acid rain

as the Earth cooled.

In this cosmic winter,

75% of all living things

perished.

When the skies cleared,

the dinosaurs had gone.

Human time span is so short,

it's hard to understand

that we will be undone by forces

that play out

over millions of years.

In Utah, the shells of countless

millions of marine creatures

which lived and died here

have been exposed

where the San Juan River

creates a great tear

in the Earth's crust.

The river has revealed

a lost world.

200 million years ago,

the shallow seas

once lapped the shores

of the giant supercontinent

Pangaea,

which stretched unbroken

from pole to pole.

50 million years ago,

this entire region underwent

a cataclysmic change.

Erosion began relentlessly

stripping away

layer upon layer of rock.

The tectonic forces

which squeezed, compressed,

and lifted the land

were locked in an endless battle

with erosional forces,

carving fantastic landscapes.

Water is the strongest force

of all.

It cuts through solid rock

to create deep canyons.

With terrible patience,

it will scour away the stone

and shape the rocks.

One day, in an unimaginably

distant future,

Antelope Slot Canyon

will be as wide and as deep

as the Grand Canyon itself.

The thousand-foot-high sandstone

pillars, buttes, and mesas

that rise above the plains

are the memorials to millions of

years of the geological battle.

But they, too, will disappear.

Nothing can withstand erosion.

Sculpting the surface,

gouging out the deepest ravines,

cutting down

the tallest mountains,

nature finds

its own equilibrium.

The small mining town

of Kolmanskop,

abandoned just

a few decades ago,

is already being invaded

by the sand dunes.

Eventually it will be

entirely covered.

If we turn our back

for one moment,

the geological cycle of erosion

and deposition will take over.

Professor Rampino knows

from his work

in the Namibian desert

how the tectonic dance will end.

Scientists may argue

about the short and medium term,

but the further ahead

they look,

the clearer the vision becomes.

The sand in this dry riverbed

in Namibia

is part of an endless cycle

of erosion and deposition.

The sand is formed by erosion

of granite outcroppings

and carried downstream

by rivers to the coast

and picked up by ocean currents,

moved along the Namibian shore

to form the long beaches

of Namibia.

Some of the sand is blown inland

to form dunes.

The sands can be

consolidated into sandstone

and then be eroded again

to form new sands,

part of a cycle from granite,

to sand, to sandstone,

and back to sand again.

On a human time scale,

not much happens.

But on a geological time scale,

all that we've done and all that

we've made will be destroyed.

So, at the end,

Earth has no future.

Through millennia to come,

the unfamiliar continents

will form and move on

as the plates continue

their wanderings.

Rivers will change

their courses,

oceans will empty and fill,

and mountains erode

and rise again.

But our sun is aging.

In 5 billion years,

it will run out of energy.

As gravity tightens its grip,

it will collapse on itself,

the temperature rising

to 100 million degrees.

It will expand uncontrollably,

engulfing Mars, Venus,

and the Earth.

The seas will boil away,

the atmosphere evaporate,

as Earth becomes

a charred ember.

Then the sun will cease

all nuclear fusion and die.

It will be the end

of our amazing Earth.

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