Answer:
At great depth within the Earth.
Step-by-step explanation:
Intrusive igneous landforms form when hot substances crystalize and are form from magma underground the Earth.
Intrusive igneous landforms originate at great depth within the Earth because they crystalises deep down below Earth surface and slowly cook to form large crystals.
The intrusive igneous landforms are formed deep below the Earth when magma cools and solidifies.