Theme: Tsunamis

 

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Text, Viewspace. The show will continue in 15 seconds. Coming up: Explore the science of tsunamis. 

 

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The text appears on a background of stars which move slowly towards and past us. 

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Text, What Is A Tsunami?

 

Tsunamis are one of the most powerful, and misunderstood, natural phenomena on our planet.

 

Neither a true tidal wave nor a single, huge rogue wave, 

 

a tsunami is a series of broad, high-speed waves generated by the sudden displacement of ocean water,

 

often by the movements of rock from an undersea earthquake

 

and more rarely by a landslide or volcanic eruption.

 

Tsunamis can also be caused by a massive meteorite falling into the ocean.

 

Energy is transferred from the moving rock to the ocean, sending waves out in all directions. Tsunamis can travel as fast as 450 miles per hour and maintain speed across entire oceans.

 

In the deep ocean these waves are barely detectable,

 

but they slow down and gain height dramatically as they move into shallower water.

 

These tall, broad waves flood coasts, moving inland like a series of rapidly rising tides or storm surges.

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Text, Myth Versus Reality. Myth, A tsunami is a giant wave.

 

Reality, A tsunami is a series of waves. In the deep ocean, tsunami waves are small in height and the distance between wave crests can be more than 100 miles. Tsunami waves get taller as they move into shallower water. The first wave is not always the largest.

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A lush green forest by bodies of water becomes brown and sickly. The North polar ice cap recedes. Text, Before and After, Flooding of Nagatsura. 

 

The Earth spins in space. Nagatsura, Miyagi, Japan is pointed out in the North western Pacific Ocean. Zooming into it, a river delta surrounded by striking red mountains. Flooding of Nagatsura, Japan, January 2011. 

 

In this infrared NASA Terra satellite image, hillside vegetation appears red and fallow farms are light brown, in contrast with the blue bay and river. 

 

Two months after this image was taken, a magnitude 9.1 earthquake shook the seafloor 80 miles off the coast. 

 

The small town of Nagatsura and surrounding farmlands were swamped by a tsunami. Farmland is highlighted along the river banks. 

 

The entire delta is filled with water in a March 2011 image. Three days later, the Terra satellite captured the devastating flooding. Steep, narrow bays like the Oppa trap and focus the energy of incoming tsunami waves. 

 

Huge volumes of water were pushed inland, nearly 30 miles up the Kitakami River. 

 

Nearly a year later, NASA's Earth Observing-1 satellite shows that the Kitakami River is back within its banks, but the farms north and east of Nagatsura have become a river bottom. A February 2012 image shows reduced water levels, except at the mouth of the delta. 

 

All three images show a side by side comparison of the impact of the tsunami.

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Two images compare an ice shelf. The first has a large area of white, and the next image has a diminished area of white.

 

Text, Before and After Sulzberger Ice Shelf.

 

A display of Earth from space. Rings highlight an area near Japan.

 

Text, March 11, 2011. As a magnitude 9.0 earthquake rocks Japan, half a world away, the Antarctic Sulzberger Ice Shelf maintains its calm watch over the Ross Sea.

 

Earthquake epicenter, Japan. Sulzberger Ice Shelf, Antarctica.

 

Overhead image of ice masses in the Ross Sea.

 

Text, The powerful earthquake triggers tsunami waves that travel 8,000 miles across the Pacific Ocean at a speed of nearly 450 miles per hour.

 

A world map with a colored scale. The Sulzberger Ice Shelf is circled at the bottom of the map. A burst of color on the map shoots out from an area near Japan.

 

Text, The waves are likely only a foot high when they arrive, but they are powerful enough to lift and flex the ice, breaking off huge icebergs.

 

An outer section of the ice shelf is highlighted. In a time lapse from March 11th, 2011 through March 16th, ice from the shelf breaks off and drifts into the sea.

 

Text, NASA and ESA satellites show that five days after the initial tsunami, two icebergs, each the size of Manhattan, had separated from the coast.

 

March 11, 2011 on left. March 16, 2011 on right.

 

Researchers had never before observed a tsunami having this effect.

 

We slowly zoom in on the ice shelf.

 

The satellite observations confirmed a tsunami's ability to alter the surface of the Earth, half a world away from its origin.

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Text, The Case of The Orphan Tsunami and The Ghost Forest 

 

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People living on the Japanese islands have kept records of earthquakes and tsunamis for more than 14 centuries. 

 

These records became key clues in solving a scientific mystery that spanned oceans and centuries. 

 

In the twelfth month of the twelfth year of the Genroku Era, the Japanese recorded an usual event, a tsunami that flooded more than 500 miles of the Pacific coastline, 

 

destroying dozens of homes and farms from Kuwagasaki to Tanabe with no ground-shaking warning beforehand. It was known as the orphan tsunami. 

 

Nearly 300 years later, researchers in the Pacific Northwest found evidence that a "ghost forest"—a once thriving woodland—had been killed by a massive inundation of saltwater. 

 

This was mysterious, because the region was not known for strong, tsunami-generating earthquakes. 

 

Unlike in Japan, the only records here were inscribed in the tree rings of the silent ghost forest, which had stopped growing after the summer of 16 99. 

 

However, people living in the Pacific Northwest had passed down accounts of disaster and survival. 

 

The Hoh Tribe says that Thunderbird and Whale had a horrible fight, shaking the mountains and causing the ocean to rise up and cover the land. 

 

The Yurok tell of Earthquake running up and down the coast, smashing down the earth so that the ocean flowed in. 

 

The Makah recall when Neah Bay was rapidly drained and then flooded, leaving canoes in the trees. 

 

The Tolowa tell of a boy and girl, sole survivors who outran the waves to a mountaintop, and remade the world alone. 

 

All along the coast, communities were passing down oral histories that matched up with the geological record. The same tsunamis that destroyed communities had created the ghost forest. 

 

The Japanese records helped fill in the blanks. By the modern calendar, the Genroku Era tsunami took place on January 26, 1700. 

 

Around 9:00 PM, built-up pressure between the Juan de Fuca and North American tectonic plates was violently released, jolting the coast from northern California to Vancouver Island. 

 

Tsunami waves spread out from the site of the earthquake. Some areas of the Pacific Northwest coast dropped as much as six feet, and the ocean surged inland. 

 

Trees that had stopped growing for the winter would never grow again. 

 

After 10 hours, the tsunami reached the coast of Japan, destroying homes and crops over a 500-mile span of coastline 

 

and puzzling a culture that was very familiar with tsunamis. 

 

By piecing together Indigenous oral histories, written records in Japanese texts, and geological clues, we now know where the mysterious orphan tsunami originated.

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Text, Sumatra 2004. A marshy valley with scattered vegetation and farmland.

 

The Earth rotates in space. Earth's surface is made of separate tectonic plates. Plate boundary lines appear around the globe, carving out the continents. Most tsunamis begin with violent movement at the undersea boundaries between these plates. A cross-section of a seabed shows two plates rubbing up against one another and slipping violently over each other. A shockwave is unleashed to the water above, creating a tidal wave.

 

While tsunamis are most common in the Pacific Ocean, which is ringed by the boundaries of tectonic plates, they can, and have, occurred in every ocean.

 

One of the deadliest natural disasters in modern history began on December 26, 2004, on the floor of the Indian Ocean. A shockwave radiates out from a plate boundary in Sumatra, Indonesia. The force of the 9.1 magnitude earthquake altered Earth's rotation and shape, and generated a world-sweeping tsunami. The wave quickly travels throughout the Indian Ocean and around the continents into the Atlantic and Pacific Oceans. Northern Sumatra was hit within 20 minutes. Because tsunamis occur less frequently in the Indian Ocean, the region had no established warning system.

 

An IKONOS Satellite Image of Aceh, Indonesia, January 10, 2003, shows a fertile, green coastline, compared to a barren, reddish brown landscape in December 29, 2004. A single building remains standing amidst the remains of a city, reduced to mud. The human toll was catastrophic. Indonesia lost more than 167,500 people. Buildings are shredded to rubble. A boat washed up in the middle of the road. People watch as an enormous dirty wave crashes through palm trees. Ao Nang, Thailand. Globally, more than 200,000 people died, including in Eastern Africa, 3,000 miles away from the epicenter. The husks of scattered houses amidst a sea of debris and muddy water. A devastate village. Xaafun, Somalia.

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Text, scientists are developing a new approach to tsunami detection and warning systems

 

Variometric Approach for Real-Time Ionosphere Observation, or VARION.

 

The high and low points of tsunami waves compress and extend the air above them, creating corresponding gravity waves in the atmosphere.

 

These waves travel upward through the air, where they affect the density of the electrons in the upper atmosphere layer called the ionosphere.

 

VARION uses the Global Positioning System (GPS) to measure these changes.

 

During the March 2011 tsunami, GPS showed that the gravity waves reach the ionosphere in 30 to 40 minutes.

 

The atmospheric gravity waves also kept pace with the tsunami's horizontal movement, moving around the globe at roughly 700 kilometers (450 miles) per hour.

 

Scientists hope that VARION and other ionosphere-monitoring missions can be used collaboratively with existing tsunami detection systems to provide early warnings to communities and save lives.