Oceanic Crust
Continental Crust
Oceanic crust is denser than continental, this is why continents are at higher elevation than oceans.
        
             
        
        
        
Answer:
great oil reserves that encourage economic activities such as oil pro- duction. ... Agriculture plays a smaller role in many countries, such ... leum or natural gas—to make fertilizers, medi- ... duction are important in both Southwest Asia and ... on the earth, producing an even greater strain on water resources
Explanation:
 
        
             
        
        
        
"<span>What contributed to the formation of the majority of Iceland?"
Lava is the answer, I believe.</span>
        
                    
             
        
        
        
Igneous rock derives it's name from the Latin word ignis which means fire. It is formed when the magma after volcanic eruption gets cool and solidified either on the surface of earth crust or inside the earth crust. These rocks are characterized by their hardness. These rocks undergoes no chemical weathering but exhibit very low mechanical or physical weathering may occur. Therefore, hardness is the property which can be used to identify the origin of an igneous rock.
        
             
        
        
        
"The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period, 419.2 Mya.<span> <span>Wikipedia."
https://www.google.com/search?q=He+Silurian+period+occurred&rlz=1C1RUCY_enUS760US760&oq=He+Silurian+...
</span></span>