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Earth's atmosphere is mostly made up of Nitrogen, Oxygen, Argon and water vapor. The Cretaceous Period is known as the last part of the "Age Of Dinosaurs." Dinosaurs are Mesozoic organisms.

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Earth's atmosphere is mostly made up of Nitrogen, Oxygen, Argon and water vapor. The Cretaceous Period is known as the last part of the "Age Of Dinosaurs." Dinosaurs are Mesozoic organisms.

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The ocean floor isn't flat as there are underwater mountain chains. Oceanic crust gets formed at the ridges. Earth expands at a slow, small rate, but it definitely does expand.

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How do we know the age of the seafloor?

Scientists can determine the age of the seafloor by examining the changing magnetic field of our planet. Every once in a while, the currents in the liquid core, which create the Earth's magnetic field, reverse themselves: it is called a geomagnetic reversal. This has happened many times throughout Earth's history.

When scientists studied the magnetic properties of the seafloor, they discovered normal and reversed magnetic stripes with different widths. These magnetic patterns are parallel to the mid-ocean ridges and symmetrical on both sides. As rocks crystallise from lava at the ridges, they literally record the magnetic field of the Earth at the time of their creation.

These stripes of normal and reverse magnetic fields with different sizes can be matched with the geomagnetic reversals records obtained from continental rocks already dated. This is how scientists determine the age of the seafloor.

How to form magnetic striping: new oceanic crust forms continuously at the mid-ocean ridges. While it cools down, it records the magnetic field during its formation. The two parts of the oceanic plate are pulled apart, and magnetic stripes become older as they move away from the mid-ocean ridge. The figure shows the spreading ridge about 5 million years ago (a), about 2 to 3 million years ago (b) and nowadays (c). Courtesy of the U.S Geological Survey.

To confirm the ages obtained with magnetic records, and get an absolute age of the seafloor, scientists use the radioactive dating technique. When the lava solidifies at the ridges to form the new seafloor, radioactive elements coming from the mantle are trapped in it. These elements, like 238U (Uranium) or 40K (Potassium) are unstable, and decay with a very precise rate to become what is called daughter products: 206P (Lead) for Uranium and 40Ar (Argon) for Potassium. By measuring the amount of remaining radioactive elements and daughter products in the seafloor, scientists can determine when the magma crystallized, and thus know the absolute age of the seafloor.

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Scientists can determine the age of the seafloor by examining the changing magnetic field of our planet. Every once in a while, the currents in the liquid core, which create the Earth's magnetic field, reverse themselves: it is called a geomagnetic reversal. This has happened many times throughout Earth's history.

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Geophysics is the physics of the Earth and its environment in space. It is also the study of the Earth by measuring things and collecting data. Sometimes geophysics means only studying the geology of the earth such as its shape, gravitational and magnetic field, internal structure and composition. It is can also mean how those create plate tectonics, magmas, volcanism and rock formation.How the earth and sun affect each other is also part of geophysics

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The temperature of the seafloor to se how old rocks are

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The ocean floor is not flat it has a sandy expansion, there is a oceanic crust, and earth is expanding very small amounts.

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The ocean floor is not flat it has a sandy expansion, there is a oceanic crust, and earth is expanding very small amounts.

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Layla Werner

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The sea floor is not flat it has little hills and even volcano's underwater, so no it is not floor. The oceans crust like hills are being formed at those ridges. The Earth is expanding slowly but surely expanding.

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The Permian time was 299 to 251 million years ago and has the largest recognition  of the largest  mass extinction recorded in history.

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The Permian time was 299 to 251 million years ago and has the largest recognition  of the largest  mass extinction recorded in history.

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Layla Werner

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The ocean floor is not flat it consists of mountain chains with a rift valley. New oceanic crust is formed at the middle of the oceans. Yes, the Earth is expanding from new land being formed from volcanic lava hardening.

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the paleogene, neogene and quaternary periods are the three periods of the cenozice era. Jurassic period is known for large plant eating dino's and some small carnivores too. the cretaceous period is known for being last of "the age of earth".

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In the Cambrian Period there was much less land on Earth. Pretty much the entire planet was water. Over time the land on Earth appeared to grow, connect, and separate.

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Geophysics is the physics of the Earth and its environment in space. It is also the study of the Earth by measuring things and collecting data. Sometimes geophysics means only studying the geology of the earth such as its shape, gravitational and magnetic field, internal structure and composition. It is can also mean how those create plate tectonics, magmas, volcanism and rock formation.

Some geophysicists now also study the hydrological cycle including snow and ice. They study how the oceans and the atmosphere move. They study electricity and magnetism in the atmosphere, ionosphere, and magnetosphere. How the earth and sun affect each other is also part of geophysics.

Geophysics was only recognized as a special area of study in the 19th century. But, there were geophysicists in ancient history. The first magnetic compasses were made in the fourth century BC and the first seismoscope was built in 132 BC. Isaac Newton applied his theory of mechanics to the tides and the precession of the equinox. Instruments were developed to measure the Earth's shape, density and gravity field, as well as parts of the water cycle. In the 20th century, geophysical methods were developed for remote exploration of the solid Earth and the ocean.

Studying geophysics may help with problems such as mineral resources, reducing natural hazards, and protecting the environment. Geophysical survey data help find petroleum reservoirs, mineral deposits, groundwater, and archaeological relics. Such data can also tell the thickness of glaciers and soils, and tell which areas have environmental damage that should be fixed.

Images for kids

A map of deviations in gravity from a perfectly smooth, idealized Earth.

A model of thermal convection in the Earth's mantle. The thin red columns are mantle plumes.

Illustration of the deformations of a block by body waves and surface waves (see seismic wave).

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Geophysics is the physics of the Earth and its environment in space. It is also the study of the Earth by measuring things and collecting data. Sometimes geophysics means only studying the geology of the earth such as its shape, gravitational and magnetic field, internal structure and composition.

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Seafloor spreading happens at the bottom of an ocean as tectonic plates move apart. The seafloor moves and carries continents with it. At ridges in the middle of oceans, new oceanic crust is created.

At the Mid-Atlantic Ridge (and other places), material from the upper mantle rises through the faults between oceanic plates. It forms new crust as the plates move away from each other. The new crust then slowly moves away from the ridge. Seafloor spreading helps explain continental drift in plate tectonics.

Earlier theories (e.g. by Alfred Wegener) of continental drift were that continents ' plowed' through the ocean. The modern idea is that the ocean floor itself moves and carries the continents with it as it expands from a mid-ocean ridge. Today, it is accepted. The phenomenon is caused by convection in the weak upper mantle, or asthenosphere.

Mid-ocean ridge

A mid-ocean ridge is an underwater mountain system. This consists of mountain chains, with a rift valley running along its spine, formed by plate tectonics. A mid-ocean ridge marks the boundary between two tectonic plates which are moving apart. A mid ocean ridge is made by a divergent boundary.

The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system that is part of every ocean. The mid-oceanic ridge system is the longest mountain range in the world. The continuous mountain range is 65,000 km (40,400 mi) long. It is several times longer than the Andes, the longest continental mountain range. The total length of the oceanic ridge system is 80,000 km (49,700 mi) long.

Mid-ocean ridges are geologically active, with new magma constantly emerging onto the ocean floor and into the crust at and near rifts along the ridge axes. The crystallized magma forms new crust of basalt and gabbro.

The rocks making up the crust below the sea floor are youngest at the axis of the ridge and age with increasing distance from that axis. New magma of basalt composition emerges at and near the axis because of decompression melting in the underlying Earth's mantle.

The oceanic crust is made up of rocks much younger than the Earth itself: oceanic crust in the ocean basins is everywhere less than 200 million years old. The crust is in a constant state of 'renewal' at the ocean ridges. Moving away from the mid-ocean ridge, ocean depth progressively increases; the greatest depths are in ocean trenches. As the oceanic crust moves away from the ridge axis, the peridotite in the underlying mantle cools and becomes more rigid. The crust and the relatively rigid peridotite below it make up the oceanic lithosphere.

Slow spreading ridges like the Mid-Atlantic Ridge have large, wide rift valleys, sometimes as big as 10-20 km wide and very rugged terrain at the ridge crest. By contrast, fast spreading ridges like the East Pacific Rise are narrow, sharp incisions surrounded by generally flat topography that slopes away from the ridge over many hundreds of miles.

Images for kids

Age of oceanic lithosphere; youngest (red) is along spreading centers

magnetic stripes formed during seafloor spreading

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Seafloor spreading happens at the bottom of an ocean as tectonic plates move apart. The seafloor moves and carries continents with it. At ridges in the middle of oceans, new oceanic crust is created. At the Mid-Atlantic Ridge (and other places), material from the upper mantle rises through the faults between oceanic plates.

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EarthViewer | This interactive module allows students to explore the science of Earth's deep history, from its formation 4.5 billion years ago to modern times.