NARRATOR: Lisbon, Portugal.
November 1, 1755.
Across the city, a celebration is underway.
Thousands of Christians are packed
into churches to celebrate a festival
known as All Saints' Day.
But then, at about 10:00 AM, without warning disaster
strikes.
MICHAEL WYSESSION: A massive magnitude
eight earthquake occurred in the Atlantic Ocean seafloor,
right along the tectonic plate boundary
between Eurasia and Africa.
The shaking from this earthquake knocked down about 85%
of the buildings of Lisbon.
Even worse, this earthquake occurred
while most people were in mass, in church or cathedrals,
on All Saints' Day.
Lisbonites are in all these churches,
and many of the most major churches in Lisbon
were destroyed.
It was one of the most devastating earthquakes
that Europe had seen in centuries.
NARRATOR: In a matter of minutes,
the massive earthquake reduced the buildings throughout Lisbon
to rubble and opened a 16-foot wide crack in the ground
through the center of the city.
Estimates place the death toll as high as 50,000
people, or about 20% of Lisbon's population.
In the early 1700s, if you had listed the five great cities
of Europe, London, Paris, Rome, you well might have
included Lisbon in that list.
But after 1755, Lisbon's glory was reduced literally to ashes.
Lisbon rebuilt, but never really reached
the same glory that it had.
NARRATOR: In the aftermath of the horrific quake,
the residents of Lisbon struggle to understand why this tragedy
had befallen their city.
Many among the Christian populace,
who had only heard of such devastation in the Holy Bible,
believed the earthquake to be an act of God.
Lisbon was dominated by the Catholic Church,
a very, very religious city.
So lots of theologians started to ponder
the meaning of this event in religious terms.
Because the fact was, this earthquake
had struck Lisbon on one of its holiest days,
the Feast of All Saints.
It had killed tens of thousands of Christians
while they were worshipping.
Why did God choose this day to bring an earthquake
upon the people of Lisbon?
And this was a confrontation for many theologians.
And they blamed the people of Lisbon.
They said, you must have been sinful.
The only reason this could have happened to you
is that you are not living by God's laws.
NARRATOR: While some people thought the earthquake was
a punishment from god, others focused
on taking practical steps to guard against such
a calamity in the future.
One of those people was Portugal's prime minister,
the Marquis of Pombal.
CHRIS MCNAB: In the reconstruction of Lisbon,
the Marquis de Pombal oversaw really critical innovations.
The first is to build earthquake resistant buildings.
These are built around wooden frames
that can actually sway with an earthquake
rather than collapse.
And then, he improves the city.
Before, it was these winding medieval streets, which
people could get blocked up in.
So the Marquis de Pombal, he redesigns
the city on a gridiron system.
So all of a sudden you have now really
wide, straight streets, which are
ideal for evacuating people.
And in fact, the way that he handled the reconstruction
of the city is the first instance of modern disaster
response in history, where someone actually
tries to take a rational response to the effects
of a natural disaster.
NARRATOR: The varied reactions to the Lisbon earthquake
have actually been quite common throughout human history.
For thousands of years, mankind has
tried to make sense of these violent tremors that
often strike without warning.
Earthquakes have a really unique
place in human consciousness because you
can't see it coming.
It's not like a giant storm that you
can see the clouds approaching, see the lightning,
hear the thunder.
Earthquakes, you feel and you hear,
but that happens in the moment.
You can't run out of the way.
There's nowhere to hide.
The problem of earthquakes and how to deal with them
goes back to antiquity.
The first seismometer to measure earthquakes
was actually invented by a scientist named
Zhang Heng, back in China, in the 21st century
of the Common Era.
This was a beautiful bronze, almost
like a cask, that had dragons around the perimeter
with balls in their mouths.
And beneath them were a little array of bronze frogs.
And the way the device worked is the pendulum inside would rock.
Just so, bumping a lever in the direction where the earthquake
occurred and a ball would fall out of the dragon's mouth
and land, telling you the orientation of an earthquake
that had happened.
And all developments since then on an earthquake detectors,
we call them seismometers, have been variations on that theme.
NARRATOR: Today's experts understand that earthquakes
happen when massive underground rocks, known
as tectonic plates, suddenly collide,
causing seismic forces to be unleashed beneath our feet.
Scientists can measure an earthquake's power,
and even pinpoint its location.
But in spite of everything we've learned,
we still have a hard time predicting
where and when the next earthquake will strike.