Did the Vedas know about the movement of "tectonic plates" which are all the continents and land masses on the Earth globe constantly moving very slowly - about 7cm a year?

The Vedas did not explain the movement of "tectonic plates" (the constant movement of land masses known as the continents) in its vast literatures, although it is a fact that all the Vedic texts have not been revealed to us. 

The concept of tectonic plates is a modern day scientific one, while ancient texts like the Vedas has explained natural phenomena such as earthquakes, through Divine intervention and actions unknown to today's limited sciences like the complex influence of karmic reactions from only the human species (karma is not created in the lower species of life) and the demigods who deliver it meaning this is not a random geological processes. 

For example, Vedic texts describe earthquakes as resulting from the movement of elevate beings like Shesha Naga, the Demigods and others advanced individual jiva-souls who help Lord Brahmā manage the material universe.

This is just like a Prime Minister who instructs and control's his many ministers who portfolios are - 

The department of water, 

The department of health,

The department of Agriculture,

The department of lands,

The department of energy, 

The department of defence,

The department of weather,

The department of education,

The department of transport,

The department of environment,

The department of oceons,

The department of forestry, 

The department of Police,

The department of housing,

etc etc.

Different in Vedic scriptures to mundane modern material science: 

In this way, ancient texts in the Vedas attribute earthquakes to the actions of the many higher demigods and advanced mystics, they are like the members in a parliament that govern the Country.

Similarly, Brahma and His millions of Demigods manage all of the temporary material universe. 

For instance, the various Demigods are the ultimate cause earthquakes and both planetary poverty and opulance based on the karmic reactions of the individual jiva-souls living in the temporary material world.

Descriptive classifications:

Other texts such as the Brihat Samhita describe why different types of earthquakes happen that are all controlled by the Demigods, such as tremors, windstorms, fires, and floods. 

They all happen as part of a higher universal plan based on the actions and reactions of the individual jiva-souls who occupy the material world and not by chance or the beliefs of foolish theories like Darwin's theory of evolution.

Modern day understanding: 

The scientific understanding of tectonic plates, which are large slabs of land mass on the surface and under the sea are constantly moving across the Earth's surface was discovered in 1912 by German Meteorologists and Geophysicist Alfred Wejener, but was ridiculed by fellow scientists. 

It took another 50 years for science to prove he was right by observing the various tectonic plates around the world through geological research.

However, Vedic scholars and devotees of Krsna explain that all such knowledge by these modern day scientists are also under the complete control of the demigods too who control everything in the material world.

As It says in Bhagavad Gita As It Is - "Not a blade of grass can move without the will of the Krsna.".=.