Its surface would look like that of the Moon, Mars or Mercury all of which do not have tectonic plates and a fixed crust.
The earth would be flat, and probably devoid of life.
If Earth's crust did not move and lacked tectonic plates, there would be no plate tectonics, resulting in no volcanic activity, earthquakes, or mountain formation. This would lead to a lack of nutrient cycling and recycling of materials, impacting the diversity and distribution of life on Earth. The absence of tectonic plates would also affect the planet's climate and potentially lead to a stagnant and inhospitable environment.
Where the different tectonic plates meet
If we didn't have tectonic plates nothing would be living. We would have been burnt by the moulten lava
They can't. Earth would be a permanently frozen planet if it wasn't for the internal heat which causes the movement of tectonic plates. And we would never have existed.
Anywhere under your feet.
When tectonic plates move and grind against each other, this is an earthquake. If the moving of tectonic plates were to occur beneath the ocean's surface, the result would be a tsunami.
While the movement of the tectonic plates can cause earthquakes, without them life on earth would not exist as we know it. The fact that Earth has tectonic plates that move has resulted in the planet ws we know it so there can be NO harm from our perspective.
If the asthenosphere stopped flowing due to cooling, tectonic plate movement in the lithosphere would likely slow down or even halt. The asthenosphere's convection currents drive the movement of tectonic plates by dragging them along as they flow. Without this driving force, the movement of tectonic plates would be significantly impacted, leading to reduced or stagnant plate motion.
That would be the lithosphere. This is broken into sections known as lithospheric (or tectonic) plates.
Those would be tectonic plates.
That would be the theory of plate tectonics.