A large crack inthe 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.
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
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 atmospherein 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.
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