Category Environtal Studies

HOW ARE FOSSILS FORMED?

When a plant or animal is buried quickly, it gets enclosed in sediment before it decomposes. As pressure transforms this sediment into rock, a hollow mould of the organism is formed. Gradually minerals seep into this hollow and harden over time to form a detailed, three-dimensional cast. Soft tissue organisms are preserved as impressions between layers of sediment. Perfectly preserved fossils of insects and other small forms of life have also been found trapped inside hardened tree sap.

The most common way an animal such as a dinosaur fossilises is called petrification. These are the key steps:

1. The animal dies.

2. Soft parts of the animal’s body, including skin and muscles, start to rot away. Scavengers may come and eat some of the remains.

3. Before the body disappears completely, it is buried by sediment – usually mud, sand or silt. Often at this point only the bones and teeth remain.

4. Many more layers of sediment build up on top. This puts a lot of weight and pressure onto the layers below, squashing them. Eventually, they turn into sedimentary rock.

5. While this is happening, water seeps into the bones and teeth, turning them to stone as it leave behind minerals.

This process can take thousands or even millions of years.

Credit: Natural History Museum

Picture Credit: Learning Geology

WHAT ARE FJORDS?

Fjords are very deep, long and narrow inlets with steep sides or sheer cliffs, seen along the coasts of Norway, New Zealand and Canada. A fjord is formed when the sea comes in to fill the U-shaped valley left by a glacier after it has retreated.

A fjord is a long, deep, narrow body of water that reaches far inland. Fjords are often set in a U-shaped valley with steep walls of rock on either side.

Fjords are found mainly in Norway, Chile, New Zealand, Canada, Greenland, and the U.S. state of Alaska. Sognefjorden, a fjord in Norway, is more than 160 kilometers (nearly 100 miles) long.

Fjords were created by glaciers. In the Earth’s last ice age, glaciers covered just about everything. Glaciers move very slowly over time, and can greatly alter the landscape once they have moved through an area. This process is called glaciation.

Glaciation carves deep valleys. This is why fjords can be thousands of meters deep. Fjords are usually deepest farther inland, where the glacial force was strongest.

Some features of fjords include coral reefs and rocky islands called skerries.

Some of the largest coral reefs are found at the bottom of fjords in Norway. They are home to several types of fish, plankton and sea anemones. Some coral reefs are also found in New Zealand. Scientists know much less about these deep, cold-water reefs than they do about tropical coral reefs. But they have learned that the living things in cold-water reefs prefer total darkness. Organisms in cold-water reefs have also adapted to life under high pressure. At the bottom of a fjord, the water pressure can be hundreds or even thousands of kilograms per square meter. Few organisms can survive in this cold, dark habitat.

Skerries are also found around fjords. A skerry is a small, rocky island created through glaciation. Most of the Scandinavian coastline is cut into thousands of little blocks of land. These jagged bits of coastline are skerries. The U.S. states of Washington and Alaska also have skerries.

Even though skerries can be hard to get around in a boat, fjords are generally calm and protected. This makes them popular harbors for ships.

Credit:  National Geographic Society

Picture Credit : Google

WHAT IS THE DEEPEST POINT ON EARTH’S SURFACE?

It’s beneath the surface of the Pacific Ocean to the southeast of Japan. There, you’ll find a deep, crescent-shaped trench. This is called the “Mariana Trench.” Near the southern tip of the crescent, there is a small slot-shaped area. This is the deepest point on Earth—Challenger Deep.

The bottom of Challenger Deep is about 36,000 feet below sea level. That’s nearly seven miles! This makes it the deepest known place on Earth.

The Challenger Deep is named after a British Royal Navy ship called the HMS Challenger. It was the first ship to measure the depths of what is now known as the Challenger Deep. The Marianas Trench in the western Pacific is 11,030 m deep.  

The trench was measured by “sounding.” This involves dropping a very long line with a weight at the end into a body of water. Today, scientists and researchers use sonar to study ocean depths.

Only four descents into the Challenger Deep have ever been achieved. The first was in 1960 by a vessel called the Trieste. The Trieste was a special kind of ship called a “bathyscaphe,” invented by Jacques and Auguste Piccard. The name “bathyscaphe” is taken from the Greek words for “deep” and “ship.”

Credit: WONDEROPOLIS

Picture Credit : Google

WHAT IS THE AVERAGE DEPTH OF OCEANS?

The average depth of the ocean is 3,700 meters (12,100 feet). But the deepest part ever recorded is located in the western part of the Pacific Ocean, in the Mariana Trench, at a depth of around 11,000 meters (36,200 feet).

Bathymetry is the scientific term for measuring the depth of water in oceans, lakes and rivers. Bathymetric maps are similar to land maps in that they show the different underwater landforms in a specific area. Scientists and researchers can use different methods to measure ocean depth.

The different methods are:

1. Sonar

The most common and fastest way of measuring ocean depth uses sound. Ships using technology called sonar, which stands for sound navigation and ranging, can map the topography of the ocean floor. The device sends sound waves to the bottom of the ocean and measures how long it takes for an echo to return. The “echo” is the sound wave reflecting off the seabed and returning to the sonar device.

2. Radar and satellite

Another alternative, though not as fast as sonar, is radar. Similar to sonar, radar requires sending out a type of wave that pings off an object and reflects back. The difference is that radar uses radio waves, a form of electromagnetic wave. But because electromagnetic waves travel slower in water compared with air and become diminished as they travel through water, they are more ideal for atmospheric measurements.

Ocean Depth Measured in the Olden Days

Before the discovery of using sound and radar to measure ocean depth, captains and their crews used a different way to measure the depth of the ocean. Sailors would use a tool called a lead line, which was essentially a lead weight attached to a rope that is marked every 6 feet, a length called a fathom, with a rag or strip of leather. A crew member would then throw the line into the water, and once the lead weight reached the bottom the sailor would measure and record the distance to the ocean floor using the strips on the rope.

The lead line was the most valuable method of measuring depth for navigation and has been used since the fifth century BCE. The tool helped sailors know how deep the water was and if their ship would run aground. The bottom of the lead weight was cupped inward and filled with grease and was used to bring up samples from the ocean floor to help sailors determine if the ocean bed was sand, gravel or mud.

Credit: NIST

Picture Credit : Google

CAN THE DEEP OCEAN FLOOR BE MAPPED?

Ocean floors are mapped using sound equipment and robot submarines. Sonar systems send out high -frequency pulses. The time it takes for the sound pulse to echo back from the ocean floor gives an idea as to the depth of the ocean.

Understanding the depth and shape of the seafloor, called bathymetry, is not only a mapping challenge but it is important if we are to better understand are oceans. This includes understanding ocean circulation, which affects climate, tsunamis, environmental change, underwater geo-hazards, resources, and many other processes affecting the environment, safety, and commerce.

Mapping the seafloor has been occurring since the early 19th century; however, obtaining accurate data has been a challenge until the invention of the sonar. More recent sonars (short fo  Sound Navigation and Ranging) provide far more accurate data, particularly when multibeam echosounder sonars are used.

The Seabed 2030 project is a project attempting to map the seafloor by 2030. Until now, however, only about 20% of the seafloor has been mapped using modern bathymetry methods. In part, the project to map the seafloor will benefit from crowd sourced data obtained from various ocean-going vessels.

However, NOAA is also leading the effort and vessels with sonar equipment are being used to map regions not often travelled by vessels. These vessels are equipped with the latest multibeam sonars that provide hydrographic surveying results that can then build detailed maps with about 0.5 meter resolution.

The mapping efforts are attempting to use different frequencies, from around 12 kHz to closer to 200 kHz, often used in shallower waters. While generally deeper sea levels are easier to map, as sound waves travel and allow a wider region to be surveyed as a ship passes by, shallow areas present challenges, given that multiple passes need to cover less area and interference observed from other sea life and vessels can disrupt data.

Credit: GIS LOUNGE

Picture Credit : Google

WHICH IS THE BIGGEST OCEAN?

The Pacific is the biggest and the deepest Ocean. It covers a third of Earth’s surface and has an area of 180 million km, holding more than 700 million km of water. It is so big that all the continents could fit within its area.

The Pacific Ocean is the largest ocean in the world, making up around 28% of the world’s surface area and almost double that in water surface area. It touches the west coast of North America. It is also home to the deepest trench on earth, the Marianas Trench, where the Challenger Deep is located. It’s 36,037 feet deep, far deeper than Mount Everest is tall. The trench is located between two tectonic plates, accounting for its incredible depth. The ocean’s coast line, along North America and Japan, is prone to earthquakes.

The ocean was named by the explorer Ferdinand Magellan. He chose “pacific” to mean “peaceful sea.” The Pacific Ocean is home to the Ring of Fire, a chain of 450 volcanoes in a u-shape. They reach from South America, along the coast of Japan, the western United States, all the way down into New Zealand. The Pacific Ocean is the world’s largest body of water.

Credit: OCEAN INFO

Picture Credit : Google