Our Dynamic Earth (IB)

How old is the solar system according to scientists?

• 3.2 billion years

• 2.1 billion years

• 4.6 billion years

• 6.5 billion years

Answer explanation

Our solar system formed about 4.6 billion years ago from a dense cloud of interstellar gas and dust. The cloud collapsed, possibly due to the shockwave of a nearby exploding star, called a supernova. When this dust cloud collapsed, it formed a solar nebula – a spinning, swirling disk of material.

Solar nebulae are formed mainly from which atoms left from the initial formation of the universe?

• Hydrogen and Helium.

• Silicon, sulfur, and phosphorus.

• Iron, magnesium, and aluminum.

• Lithium and Magnesium.

Answer explanation

The solar nebula was the rotating, flattened disk of gas and dust from which the solar system originated ∼4.6 Ga. Much of the motivation for cosmochemical studies of meteorites, comets, and other primitive bodies stems from the desire to use the results to constrain or otherwise illuminate the physical and chemical conditions in the solar nebula, in the hope of learning more about the processes that led to the formation of the planets. In addition to cosmochemical studies, there are important lessons to be learned about the planet formation process from astrophysical observations of young stellar objectsand their accompanying protoplanetary disks, from the discovery of other planetary systems, and from theoretical models.

What process led to the formation of asteroids?

• Asteroids are created by the gravitational pull of black holes.

• Asteroids formed from leftover material in the early solar system.

• Asteroids are remnants of ancient stars that exploded.

• Asteroids are formed from the collision of planets.

Answer explanation

Asteroids are rocky objects primarily found in the asteroid belt, a region of the solar system that lies more than 2 ½ times as far from the Sun as Earth does, between the orbits of Mars and Jupiter. These objects are sometimes called minor planets or planetoids. They are likely the leftovers from the early formation of the solar system and their composition may shed light on what the early solar system was like. They probably formed from the protoplanetary disk that surrounded the Sun but never had enough mass to form into the roughly spherical shape required to be considered a planet. Despite thousands having been discovered, their total collective mass is still far less than the mass of the Earth.

What happens when more particles collide and collect?

• More collisions will cause particles to break apart.

• Particles will disappear completely after colliding.

• Particles will only move faster without any aggregation.

• More particles colliding and collecting can lead to the formation of larger structures or aggregates.

Answer explanation

What role do supernova explosions play in the formation of solar systems?

• Supernova explosions create black holes that absorb all nearby matter.

• Supernova explosions enrich the interstellar medium with heavy elements and trigger star formation.

• Supernova explosions have no impact on the formation of solar systems.

• Supernova explosions only occur in galaxies far from our solar system.

Answer explanation

A supernova is the biggest explosion that humans have ever seen. Each blast is the extremely bright, super-powerful explosion of a star. One type of supernova is caused by the “last hurrah” of a dying massive star. This happens when a star at least five times the mass of our sun goes out with a fantastic bang!

Massive stars burn huge amounts of nuclear fuel at their cores, or centers. This produces tons of energy, so the center gets very hot. Heat generates pressure, and the pressure created by a star’s nuclear burning also keeps that star from collapsing.

A star is in balance between two opposite forces. The star’s gravity tries to squeeze the star into the smallest, tightest ball possible. But the nuclear fuel burning in the star’s core creates strong outward pressure. This outward push resists the inward squeeze of gravity. They have also learned that stars are the universe’s factories. Stars generate the chemical elements needed to make everything in our universe. At their cores, stars convert simple elements like hydrogen into heavier elements. These heavier elements, such as carbon and nitrogen, are the elements needed for life.

How did the moon come into being?

Answer explanation

Earth's Moon is thought to have formed in a tremendous collision. A massive object ― named Theia after the mythological Greek Titan who was the mother of Selene, goddess of the Moon ― smashed into Earth, flinging material into space that became the Moon.

The Earth spins on a tilted axis of?

Answer explanation

The axis of rotation of the Earth is tilted at an angle of 23.5 degrees away from vertical, perpendicular to the plane of our planet's orbit around the sun.

The tilt of the Earth's axis is important, in that it governs the warming strength of the sun's energy.

Which among the following elements are found at the centre of the Earth?

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Answer explanation

Deep inside Earth, near its center, lies Earth's core which is mostly made up of nickel and iron. Above the core is Earth's mantle, which is made up of rock containing silicon, iron, magnesium, aluminum, oxygen and other minerals.

Observe the image and choose the correct option from the ones given below.

• Carbon-dioxide is formed due to photosynthesis

• Oxygen is the by-product of respiration in animals

• Nitrogen is the least among the atmospheric gases

• Oxygen was formed by cyanobacteria 3.5 BYA

Answer explanation

When our solar system began to form some 4–5 billion years ago, it apparently consisted of a number of solid components with some accompanying gas. The system was held together by gravity. There was little or no free oxygen in the gas which is thought to have been a mixture of nitrogen, hydrogen, helium, methane, and some other elements of low atomic numbers. This situation continued over millions of years as our solar system with its eight planets (and Pluto) gradually evolved but without any significant amounts of atmospheric oxygen. This initial oxygen was brought about by the emergence of a family of microorganisms called cyanobacteria. Cyano means blue, and these cells have a blue‐green coloring. The origin of these organisms is not known. However, these cells had the capability of photosynthesis that is they could conserve and exploit the energy from light. To do this they contained photosynthetic pigments related to chlorophyll which is well known because of its critical role in the metabolism of plants. In fact, the chlorophyll of plants that we see today is believed to have evolved from these pigments in cyanobacteria.

Which image from the following signifies the significant event which occurred during the Cretaceous period?

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Answer explanation

The Cretaceous-Palaeogene extinction 66 million years ago is possibly the most famous mass extinction event. It was caused by a large asteroid crash-landing off the coast of Mexico, which changed the climate of the planet dramatically.

'It vapourised carbonate and sulphate rocks, which caused acid rain, and threw lots of ash, dust and dirt into the atmosphere, blocking out the Sun. This caused a global collapse of the food chain,' explains Susie.

'There also would have been a thermal heat pulse that caused wildfires - that's evidenced by charcoal in the rock record - and huge tsunamis washed across the ocean basins.'