Answer:
mountain and coastal plains
Step-by-step explanation:
According to the question, a hiker crosses a topography near the sea which has low elevation and low relief and proceeds to climb steeply to reach a peak. 
The two landforms the hiker experienced are mountain and coastal plain. 
A coastal plain is a flat, low-elevation land which is close to the sea. 
A mountain is an elevated land form that has a peak and is higher and more difficult to climb than a hill.