THE EARTH’S OLDEST ROCKS

All the major continents contain a core of very old rocks fringed by younger rocks. These cores, called Precambrian shields, are all that remain of the Earth’s oldest crust. The rocks in these shields are mostly metamorphic, meaning they have been changed from other rocks into their present form by great heat and pressure beneath the surface; most have been through more than one metamorphism and have had very complex histories. A metamorphic event may change the apparent radiometric age of a rock. Most commonly, the event causes partial or total loss of the radiogenic daughter isotope, resulting in a reduced age. Not all metamorphisms completely erase the radiometric record of a rock’s age, although many do. Thus, the radiometric ages obtained from these oldest rocks are not necessarily the age of the first event in the history of the rock. Moreover, many of the oldest dated rocks intrude still older but undatable rocks. In all cases, the measured ages provide only a minimum age for the Earth.

So far, rocks older than 3.0 billion years have been found in North America, India, Russia, Greenland, Australia, and Africa. The oldest rocks in North America, found in Minnesota, give a U-Pb discordia age of 3.56 billion years. The oldest rocks yet found on the Earth are in Greenland, South Africa, and India. The Greenland samples have been especially well studied. The Amitsoq Gneisses in western Greenland, for example, have been dated by five different methods within the analytical uncertainties, the ages are the same and indicate that these rocks are about 3.7 billion years old.

2010 HAITI EARTHQUAKE....

The 2010 Haiti earthquake was a catastrophic magnitude 7.0 Mw earthquake. Its epicentre was near the town of Léogâne, approximately 25 km (16 miles) west of Port-au-Prince, Haiti's capital. The earthquake occurred at 16:53 local time (21:53 UTC) on Tuesday, 12 January 2010.[3][4] By 24 January, at least 52 aftershocks measuring 4.5 or greater had been recorded.[5] As of Feb. 12, an estimated three million people were affected by the quake;[6] the Haitian Government reports that between 217,000 and 230,000 people had been identified as dead, an estimated 300,000 injured, and an estimated 1,000,000 homeless. The death toll is expected to rise.[7][8] They also estimated that 250,000 residences and 30,000 commercial buildings had collapsed or were severely damaged.[9]

The earthquake caused major damage to Port-au-Prince, Jacmel and other settlements in the region. Many notable landmark buildings were significantly damaged or destroyed, including the Presidential Palace, the National Assembly building, the Port-au-Prince Cathedral, and the main jail. Among those killed were Archbishop of Port-au-Prince Joseph Serge Miot,[10] and opposition leader Micha Gaillard.[11][12] The headquarters of the United Nations Stabilization Mission in Haiti (MINUSTAH), located in the capital, collapsed, killing many, including the Mission's Chief, Hédi Annabi.[13][14]

Many countries responded to appeals for humanitarian aid, pledging funds and dispatching rescue and medical teams, engineers and support personnel. Communication systems, air, land, and sea transport facilities, hospitals, and electrical networks had been damaged by the earthquake, which hampered rescue and aid efforts; confusion over who was in charge, air traffic congestion, and problems with prioritisation of flights further complicated early relief work. Port-au-Prince's morgues were quickly overwhelmed; tens of thousands of bodies were buried in mass graves.[15] As rescues tailed off, supplies, medical care and sanitation became priorities. Delays in aid distribution led to angry appeals from aid workers and survivors, and some looting and sporadic violence were observed.

On 22 January the United Nations noted that the emergency phase of the relief operation was drawing to a close, and on the following day the Haitian government officially called off the search for survivors.

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5 TIPS ON HOW TO PREPARE FOR EARTHQUAKE

Earthquakes are natural disasters that we should learn to live with, not in fear of. Learning how to prepare for an earthquake not only makes you a bit safer, it ensures that those around you are a bit safer as well.


Earthquake Preparing Tips

1. Practice earthquake drills with your family.

2. Check if your insurance covers earthquake damage.

3. Take classes in First Aid and CPR.

4. Have two designated places your family can meet after the earthquake.

5. Make an earthquake kit with basic food, shelter and water.

TALKING ABOUT EARTHQUAKES...

It seemed like Mother Nature was avenging herself on us who have used all her endowments to the fullest extent without caring to rejuvenate them. Here we would try to find out the causes of earthquakes so that we can all contribute to the prevention of such things in our own small ways. Individual awareness would definitely lead to mass awareness.

                              Causes of earthquakes

If seen broadly we can say that earthquakes are caused due to two major reasons. The first reason is the eruption of volcanoes, which are sudden, and as is known volcanoes are seat of inner disturbance and can effect the plates which is the second cause of earthquakes. Earthquakes are caused due to disturbance in the movement of plates, which again can be caused due to various reasons like under crust waves or cracks in the plates.

                          Plate Tectonic Theory

The outer layer of the earth is divided into many sections known as plates, which are floating on the molten magma beneath the earth’s crust. Now the movement of these plates is determined by the convection current in the molten magma. The heat makes these plates rise and vice versa. Therefore after intervals there are plates that get submerged in the molten magma and there plates that rise upwards and at times even new crust is formed from the molten magma which in turn forms a new plate until it connects itself with the already existing ones. At times these plates and can be pushed up to form mountains and hills and the movement is so slow that it is really hard to comprehend that there is any movement at all. The movement and the results come out to be visible suddenly. Now these plates are the bases on which the continents stand and when these plates move the continents also move. Most of the earthquakes occur on the edges of the plates where a plate is under one or across. This movement disrupts the balance and position of all plates, which leads to tremors, which are called earthquakes.

                                      Volcanic Eruptions

When volcanoes erupt it is because the molten magma under the crust of the earth is under enormous pressure and to release that pressure it looks for an opening and exerts pressure on the earth’s crust and the plate in turn. A place, which is the seat of an active volcano, is often prone to earthquakes as well because the pressure that is exerted by the magma exceeds the limit these plates move and that causes earthquakes. Earthquakes are also caused after a volcanic eruption since the eruption also leads to a disturbance in the position of plates, which either move further or resettle and can result into severe or light tremors.

The excessive exploitation of earth’s resources for our own benefits like building dams to store large volumes of water and blasting rocks and mountains to build bridges and roads is also the reason behind such natural disruptions.