Where is the Youngest and Oldest Crust?

What is meant by Crust? What is Rock Cycle? What is the Composition of Oceanic Crust? Where is the Oldest and Youngest Oceanic Crust found? Is the Youngest Layer near the Ridge? 
where is the youngest and oldest crust
Image by Ben Kerckx from Pixabay

Do you know how old our Earth is, and who resided on it at the beginning? Our Earth is estimated to be 4.543 billion years old and microbes (microscopic organisms) have been residing on it since the beginning of time. Since then, the Earth has been developing and changing, which includes the formation of the crust too. So, what crust is and where is the youngest and oldest crust on the Earth? Have you heard where is the oldest seafloor crust? If not, then we will tell you.

1. What is meant by Crust?


In terms of Earth, a crust is referred to as the outermost solid layer of a planet or other celestial body. However, here we are referring to the hardened layer, deposit, or coating on the surface of the Earth or beneath water bodies like oceans and seas. (See What is the Difference between Oceanic Crust and Continental Crust?)

2. How are Crusts formed?

At the beginning of the Earth, there have been various volcanic activities leading to the formation and deformation of landscapes. It is said by the scientist that after the accretion (the phase of final addition of Earth’s mass) a large amount of heat was retained by the Earth. It melted the upper mantle and formed the magma ocean that covered the Earth. In the coming years, Earth cooled down leading to the cooling of the magma ocean. It crystallized the magma and a widespread crust was formed. Must read What Layer of the Earth does Magma come from?

3. What is Known as Rock Cycle?

where is the youngest and oldest crust 2
Photo by Jeremy Bishop on Unsplash

The transition of rocks from one type of rock to another over a period of million years is termed the rock cycle. The initial stage is the igneous rocks that are formed after the magma cools and crystallize. Then it enters the 2nd stage, which is sedimentary rocks that are formed as a result of the continuous deposition of the sediments on them.
Lastly, metamorphic rocks are formed when any of the two forms of the rock is exposed to extreme heat and pressure. This is the same process as the formation of crusts. Trying to find where is the youngest and oldest crust? We will come to that. (See What are the Uses of Rocks?)

4. What are Types of Crusts on Earth?

Based on their thickness and age, the crust on the surface of the Earth is divided into 2 types.

  • Continental Crust: It is the layer of igneous, sedimentary, and metamorphic rocks that form areas of shallow seabed near the shoreline. You know them by the name of islands and continents but the layer covering these pieces of land is termed the continental crust.
  • Oceanic Crust: The uppermost layer of the oceanic portion of the tectonic plates is termed the oceanic seafloor crust. It is lying on the uppermost layer of the rigid mantle and is divided into three layers.

5. What is the Composition of Oceanic Crusts?

The ocean layers are made up of different layers with varying thicknesses and compositions.

  • Layer 1 – It is made up of semi-consolidated sediments that are thicker away from the ridge. Its thickness is on average 0.4 kilometers, and it is the top layer in the ocean bed.
  • Layer 2 – This layer is divided into 2 layers and called layer 2A and layer 2B. Layer 2A is the upper layer of the two containing basalt that is glassy to fine, mostly known as pillow basalt. The lower layer 2B is made of diabase dikes (a sheet of rock formed in the fractures of the pre-existing rock body).
  • Layer 3 – It has a thickness of about 5 km below the point it begins. About two-thirds of the oceanic crust volume comes from this layer. It is the lowermost layer in the ocean bed which was formed by the slow cooling of the magma lying below the surface of the Earth. It is composed of cumulate ultramafic rocks and coarse-grained gabbro.

6. Where is The Youngest and Oldest Crust?

Earth’s crust is covered with different types of rocks like sedimentary, igneous, and metamorphic. So, where is the youngest and oldest crust? Igneous rocks are considered the oldest because they were formed as a result of the crystallized magma ocean. Most of this old crust is now lost as a result of the shifting of tectonic plates and has been buried into the Earth.

However, the present layer on the Earth is considered the youngest which can be about 600 million years old. (See 3 Agents of Metamorphism)

7. Where is the Oldest Seafloor Crust?

Scientists mention that millions of years ago the entire surface of the Earth was a seabed which later turned into islands with a subsequent decrease in water level over the years. According to geologists, there is a stretch of the eastern Mediterranean Sea lying between Crêpe, Cyprus, and Egypt that is among the oldest seafloor crusts. This region is known as the Herodotus Basin and is considered to be 340 million years old. (See What Landform is created when Two Continental Plates Collide?)

8. Where is The Crust the Youngest?

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Photo by Andrés Dallimonti on Unsplash

The ocean bed that is the youngest is near the mid-ocean ridge. According to scientists’ estimates, fresh magma is brought to the surface through some ridges. This led to the formation of this crust. This layer is denser, but not as thick as the older layers. (See What is the Most Expensive Rock in the World?)

9. How to identify the Youngest Oceanic Crust on a Map?

I guess you would like to know the trick to finding where is the youngest and oldest crust on a map. If you are observing the region on the map, look for the red regions along the ocean ridges. Yes, these red regions that are located along the ocean ridges are the youngest crust. While if you are looking for the oldest crust, look for the regions that are far from the ocean ridges. 

So, today you got to know where is the youngest and oldest crust i.e. where is the crust the youngest or oldest. One is near the oceanic ridges while the other is away from them. Share this article with your friends if you find it informative and interesting. (Also read What are Some Map Distortion Examples?)

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