As per Continental theory of Wegener the 'Opening of tethys' phase took-place due to :

Question

Accepted Answer

According to Wegener's Continental Drift theory, the 'Opening of Tethys' phase occurred due to **Differential gravitational force and force of buoyancy (Option 3)**. Here's why:

*   **Differential Gravitational Force and Force of Buoyancy:** Wegener proposed that the continents, composed of "sial" (silica and aluminum), were floating on a denser "sima" (silica and magnesium) layer. The differential gravitational force (the varying gravitational pull on different parts of the Earth) combined with the buoyant force (the upward force exerted by the denser sima on the less dense sial) caused the continents to drift. This drift, specifically the movement of landmasses away from each other, led to the formation and widening of the Tethys Sea. The differential gravitational force acted unevenly on the continental masses, and the buoyancy allowed them to move through the underlying sima. This combination of forces is what Wegener believed was responsible for the breakup of Pangaea and the subsequent opening of the Tethys Sea.

Now, let's examine why the other options are incorrect according to Wegener's theory:

*   **Tidal force of the moon (Option 1):** While tidal forces exist, Wegener argued against them being the primary driver of continental drift. He calculated that the tidal forces required to move continents would be so immense that they would stop the Earth's rotation. Therefore, tidal forces of the moon were deemed insufficient to cause continental drift and the opening of the Tethys Sea.

*   **Tidal force of the sun (Option 2):** Similar to the moon's tidal force, the sun's tidal force is also insufficient to generate the immense forces required to move continents across the Earth's surface. Wegener dismissed this as a viable mechanism for continental drift.

*   **Separation of moon from the earth (Option 4):** The separation of the moon from the Earth is a very early event in Earth's history and is not directly related to the breakup of Pangaea or the opening of the Tethys Sea, which occurred much later in geological time. Wegener's theory focused on forces acting on the continents *after* the Earth and Moon had already formed. The separation of the moon is not a mechanism that explains the ongoing process of continental drift.