You're asking about the pressure of the Earth's crust at its bottom, which is the boundary between the crust and the mantle, known as the Moho discontinuity.

Here's what we know:

* Pressure increases with depth: The deeper you go into the Earth, the more weight is pushing down on you from the layers above. This causes a significant increase in pressure.

* Moho depth varies: The Moho is not a perfectly flat layer. It is shallower under the oceans (around 5-10 km) and deeper under continents (around 30-70 km).

* Estimating pressure is complex: Calculating the exact pressure at the Moho requires knowledge of the density of the rocks above it, which can vary considerably.

Instead of giving a specific number, here's how we can think about the pressure at the Moho:

* It's enormous: The pressure at the Moho is many thousands of times greater than the pressure at sea level.

* It varies: The pressure will be higher under thicker continental crust and lower under thinner oceanic crust.

To get a more precise answer, you would need to:

1. Know the exact location: The Moho's depth at a specific point.

2. Model the density of the rocks above: This involves understanding the composition and structure of the crust.

In summary, the pressure at the bottom of the Earth's crust is immense and varies depending on the location. It's a complex calculation that requires detailed geological information.