Author: Sharulatha Neru

SUPERNOVA

| Sharulatha Neru
The explosion of stars towards the end of their lives is extraordinary; there is a sudden increase in their brightness and an enormous release of energy. This is a ‘supernova’ and it releases in 10 secs and 10 times the power than the Sun releases in its entire life. After a star’s detonation, a gaseous remnant remains and this expands and shines for millions of years throughout the galaxy. It is estimated that two supernovas explode each century in the Milky Way. 
Image shows supernova explosion
Image shows supernova explosion

In 1604, Johannes Kepler discovered the last observed supernova in the Milky Way. NASA’s Chandra telescope discovered the remains of a more recent supernova. It exploded in the Milky Way more than a hundred years ago.

NASA scientists use different types of telescopes to look for and study supernovas. Some telescopes are used to observe the visible light from the explosion. Others record data from the X-rays and gamma rays that are also produced. Both NASA’s Hubble Space Telescope and Chandra X-ray Observatory have captured images of supernovas.

Rivers

| Sharulatha Neru

Some rivers begin high up in mountains, where snow collects and melts. Some rivers begins where underground springs bubble up to the surface. All rivers run downhill, carrying fresh water to the sea.

river erosion

A river gradually erodes the land it crosses. It slowly carves a V-shaped valley as it travels, wearing down rock and earth and carrying the particles in the waters. One of the best examples of a river changing the landscape is the Grand Canyon in the Colorado, USA. It has taken around 17 million years for the Colorado River to carve the canyon from rocks.

Photo by David Ilécio on Pexels.com.

Creating new land

A river slows down as it gets nearer to the sea and the ground becomes flatter. When a river slows the particles of earth and rock it is carrying drop to the bottom as sediment, creating mudflats and islands. Sometimes these spread out at the river’s mouth in a wide area called a delta. The Ganges and the Brahmaputra rivers meet in India and Bangladesh to form the world’s largest delta, stretching over an area of 105 000km.

the world’s waterfalls

If a river reaches a very hard band of rock, it will wear down the softer rock on the other side and end up plunging down as a waterfall. The world’s highest waterfall is the Salto Angel Falls in Venezuela, which plunges 807m over a cliff. One of the world’s largest falls is Victoria Falls on the African Zambezi River. Over time the Zambezi has carved out a channel around, 1 007m wide.

FACTS…FACTS…FACTS!!!

Top five rivers in order of length

  1. Nile River, Africa (6 696km)
  2. Amazon River, South America (6 400km)
  3. Yangtze River, Asia (6 240km)
  4. Mississippi River, North America (6 192km)
  5. Ob River, Russia (5 534km)
Photo by Mads Thomsen on Pexels.com

EARTHQUAKES

| Sharulatha Neru

Earthquakes causes the ground to shake, and occur when there is a sudden movement in the Earth’s crust. They happen in areas where two of the Earth’s plates meet under the ground

Earthquakes closely follow the borders of the Earth’s plates.

earthquake areas

Most earthquakes occur around the edges of the Pacific Ocean or in mountainous areas such as the Himalayas. It is here that the plates under the Earth’s surface are pushing or sliding the most. Scientist monitor these areas to try to predict earthquakes, measuring for possible warning signs- such as minor tremors that might build up to a larger event.

measuring earthquakes

Instruments called seismographs measure earthquakes. A seismograph detects the shock waves produced and displays a line that records how strong each wave is.

FACTS…FACTS…FACTS!!!

The Richter Scale has 10 numbers representing the energy produced by an earthquake. Each number represent 10 times more energy than the previous number.

SCALE EFFECTSFREQUENCY
0 – 2.0 Not Felt 8 000 a day approx.
2.0 – 2.9 Not felt but recorded 1 000 a day approx.
3.0 – 3.9 Felt but no damage 49 000 a year approx.
4.0 – 4.9 Felt slightly indoors 6 200 a year approx.
5.0 – 5.9 Weak buildings might fall800 a year approx.
6.0 – 6.9 Destructive up to 160km away 120 a year approx.
7.0 – 7.9 Severe damage in large area 18 a year approx.
8.0 – 8.9 Severe damage over 1 000km 1 a year approx.
9.0 – 9.9 Devastation up to 10 000km 1 in 120 years approx.
10 Has never been recorded
Shows seismograph readout.

Mountains

| Sharulatha Neru

Mountains are giant masses of rocks at least 600m high. They cover about a quarter of the Earth’s surface and are usually found in groups called ranges.

Photo by Denis Linine on Pexels.com.

Mountain building

The world’s tallest mountain ranges were formed when two of the Earth’s plates collided with each other, slowly pushing up the Earth’s surface. The process of mountain formation takes millions of years and is still going on today. The highest mountain range of all, the Himalayas, first began to form about 70 million years ago and still is rising about 1cm every year.

Mount Everest in the Himalayas, a range of fold mountains.

mountain shapes

Mountains are in different shapes. It all depends on how they formed. Fold mountains are created when rock folds upwards. Fault-block mountains form when giant blocks of rocks are pushed up. Dome mountains are pushed upwards by magma bulging from below. Plateau mountains are made when a wide section of flat land is pushed up.

A dome mountain in the Adirondacks, USA.

Mountain Profile

At the bottom of a mountain there might be trees, but at some point it becomes impossible for them to grow. The place where they stop is called the tree line. Above it only tough plants such as mosses can grow. Higher still, no plants survive and there is often snow all year round. The line between where snow melts in summer and stays put all year round is called the snow line

The tallest mountain on the planet is Mauna Kea, a volcano in the Pacific Ocean. It stands 10, 203 m tall, though it rises only 4, 205m above the sea. Meanwhile Mount Everest is the highest land peak, rising 8, 848m high.

Human Skin

| Sharulatha Neru

Skin

Skin is the largest organ in the body. It is stretchy, waterproof and packed with nerves that carry messages to the brain. Skin act as out first defense against bacteria and other harmful substances.

how skin heals

Image shows stages of wound healing

As soon as your skin is cut, your body springs into action.

  1. Blood starts to clot to stop the bleeding and forms a scab to protect the wound.
  2. Beneath the surface, white blood cells attacks any germs that might have got into the cut.
  3. New skin begins to form, starting from the outside edges and spreading towards the center.
  4. When the skin has heeled, the scab dries up and falls off.

SKIN MELANIN

Melanin is a chemical that is produced in the epidermis. It gives our skin its colour. When our skin is exposed to the sunlight, the cells make more melanin to protect it from the Sun’s ultraviolet (UV) rays.

  • Fair-skinned people have the least melanin. They often get freckles, which are small spots of melanin.
  • People with olive skin produce a medium amount of melanin.
  • Dark-skinned people have lots of melanin producing cells.