All the riddles are pretty easy anyway, but here's the answer for those who are struggling (me)
Between two mountains, I often reside
A depression where the river glides
Steep slopes are found on either side
A place of beauty, nature’s pride
Answer: valley
In a geyser I reign supreme
Coming out in a heated stream
In an engine I am power
Rising up like a tower
Answer: steam
In battle, I’m a protective shell
Temple and crown, I'll guard it well
I can be leather, I can be steel
I protect you from a blow which kills
Answer: helmet
I have leaves, but I’m no plant
Beneath my cover, knowledge I grant
I have a spine, but I’m no person
Whether I discuss fact or fiction
Answer: book
I bring beautiful hues to nature’s space
I am a symbol of love and grace
I might be found in field or vase
Making the world a fragrant place
Answer: flower
I’ll always follow the streak of light
Echoing in the stormy night
Nature’s fury, forceful and vast
That comes in a sudden blast
Answer: thunder
I follow you as you move around
Yet I do not make a sound
Light is needed when I’m present
Yet darkness is my element
Answer: shadow
Between two mountains, I often reside
A depression where the river glides
Steep slopes are found on either side
A place of beauty, nature’s pride
Answer: valley
In a geyser I reign supreme
Coming out in a heated stream
In an engine I am power
Rising up like a tower
Answer: steam
In battle, I’m a protective shell
Temple and crown, I'll guard it well
I can be leather, I can be steel
I protect you from a blow which kills
Answer: helmet
I have leaves, but I’m no plant
Beneath my cover, knowledge I grant
I have a spine, but I’m no person
Whether I discuss fact or fiction
Answer: book
I bring beautiful hues to nature’s space
I am a symbol of love and grace
I might be found in field or vase
Making the world a fragrant place
Answer: flower
I’ll always follow the streak of light
Echoing in the stormy night
Nature’s fury, forceful and vast
That comes in a sudden blast
Answer: thunder
I follow you as you move around
Yet I do not make a sound
Light is needed when I’m present
Yet darkness is my element
Answer: shadow