East African Rift is Growing Quickly

A large crack in the surface of the earth, several kilometres long,   has caused a highway to collapse in Kenya. The area lies on the East African Rift, where the Arabian and African plate meet.

The earth’s crust is broken up into several tectonic plates which are constantly on the move, gliding towards or against each other at various speeds. When these plates collide energy is set free, resulting in earthquakes and volcanic eruptions.

The East African Rift stretches over 3000 km from the Gulf of Aden in the north to Zimbabwe in the south.  It consists of several valleys that are filled with long lakes. Because the two plates are moving away from each other Eastern Africa will be separated from the rest of the continent.

A rift is the first phase of a plate that is breaking apart. After millions of years, it can lead to the formation of a new ocean.  A well-known example is a separation of Africa and South America and the creation of the Atlantic Ocean.

Where the earth’s plates move away from each other magma plumes come up through the mantle and cause volcanic activity. Forces are so strong that the plate breaks apart and causes major earthquakes. In many cases, plates move slowly, at a rate of only  a few cm per year and most of the time we don’t notice these movements.

East African Rift from outer space
East African Rift from outer space – Image: Christoph Hormann

Words

  • at a rate = how fast something happens
  • collapse = fall apart; break down
  • collide = crash into each other
  • consist of = is made up of
  • constantly = always
  • crack = a line that you see when something starts to  break apart
  • crust = the hard, outer layer of the earth
  • forces = here: the power or strength of an activity
  • formation = when something new is created
  • earthquake = a sudden shaking of the earth’s surface that can cause a lot of damage and kill people
  • eruption = if something  breaks out suddenly
  • glide = move slowly and quietly
  • magma plumes = hot melted rock from the inner part of the earth which comes to the surface
  • major = here: very strong
  • mantle = part of the earth below the crust
  • notice = to see something happen; to be aware of something
  • resulting in = something that leads to something else
  • separate = divide, split apart
  • several = a few
  • stretch = to spread from one place to another
  • surface = here: the top layer of the earth
  • tectonic = about the movments of sheets of rock that form the earth’s surface
  • various = different

 

The Earth’s Hum – A Mysterious Noise

For the first time, scientists have recorded a humming sound that the earth has probably been producing for a long time. Scientists have been aware of the hum for decades, but for the first time, a team of experts have actually been able to record it

57 seismometers were placed over millions of square kilometres of the Indian Ocean.  Ultralow radio frequencies were recorded on the ocean’s floor

For some time, geologists have pointed out that the earth is not silent but vibrates almost everywhere. However, it is a sound with a frequency thousands of times lower than what the human ear can hear.

Scientists don’t know what causes the earth’s hum but could learn more by getting a clearer audio signal. There are a few theories about where the sound may come from. Some say that it’s the echo of waves crashing onto the coast, while others think that it may be the atmosphere in motion. Geologists, however, agree that the sound does not come from earthquakes because it is continuous.

In 1998 Japanese scientists proved that the earth’s hum was real, but nobody has been able to record it until now. Geologists hope that by analysing the recording they can get more information on the interior structure of the earth.

 

Seismometers record all kinds of noises and disturbances on the surface of the earth
Seismometers record all kinds of noises and disturbances on the surface of the earth

Words

  • agree = to have the same opinion
  • analyse = look at very closely in order to get more facts
  • atmosphere = the mixture of gases that surrounds a planet
  • audio signal = sound
  • aware = to know that something exists
  • cause = the reason for something
  • continuous = when something goes on all the time
  • crash = to hit something very hard
  • decade = ten years
  • earthquake = a sudden shaking of the earth’s surface that causes a lot of damage
  • geologist = person who studies rocks and how they make up the surface of the earth
  • humming = a steady low sound
  • in motion = moving
  • interior structure = what something consists of, or what it is made up of inside
  • place =  put, install
  • point out = to say how important something is
  • radio frequency = waves that are produced when you send out a radio signal
  • record = information about something that is written down or stored on a computer
  • seismometer = machine that measures how the ground moves
  • vibrate = to shake quickly and steadily in very small movements