Magma magic example tree.
Lurking not so deep beneath the earth is the fiery heart of the planet. Here its so hot that not even earth can resist its heat and becomes one with it... liquid stone born in fire... Magma magic is naturally fear inspiring for its huge damage capacity even at low levels. Its so damaging that most wizards stick to the Ethereal creation spells to avoid burning themselves. Nothing, apart from fire elementals can resist magma. Nothing.
 

1 Point magma magic.

  
Spitfire
(Ethereal creation)
 A magical sphere of molten stone is summoned into the casters hands, the caster feels no heat despite that fact that their clothes may ignite or singe from the spell.(Note the fire this spell creates is also Ethereal.) The sphere is thrown and splatters against whatever it hits in a flaming mass of molten stone. (Which is what it is.)
Solid fire enchant
(Bless/Curse)
A touch on a weapon allows the caster to pass onto that weapon both resistance to heat and a fiery blade. A weapon carrying this temporary enchantment has two advantages over its non enchanted form. The first is the fact that its hot enough to melt stone at its tip while cool enough to hold at its handle. This means that dragging it along the ground will ignite anything flammable there. The second advantage is that is sears as it damages using this heat causing great amounts of pain.
Burning river
(Summon Elemental Spirit)

Bursting up from the earth a slow fissure of magma is created which begins pouring down a slope and spreading towards the target. The magma created is not ethereal so it does extreme damage. Why is this spell so low on the list? Its VERY very slow. The magma river has a cruising speed of an unfit man walking up a hill. It gets slower as time goes on too.
Meteor
(Ethereal creation)
 A sphere of stone wrapped in fire, filled with the gooey heated goodness of a magma burst. This thing falls from the sky like a dodgeball from heck crushing whatever it hits with kinetic stone damage before bursting out into a fiery magma mass. Only one can be summoned at a time however the effects of the magma on the ground can last for hours after another is created.

2 Point magma magic.

  
The ground beneath trembles and breaks as a super heated tendril of stone reaches up from the core. This spell may be slow and very easy to avoid however the consequences of using it can be catastrophic. Once the spell is over the column of magma remains and depending on luck its possible to become a proper volcano over time.
Ground devour
(Summon element)
Fired from the hands the caster launches a bean roughly as wide as they are tall. The beam is like a pure red light and is very draining on the mana. Whatever becomes engulfed in the beam will start to super heat and explode, stones etc. will melt. People are torn up from their own heat. Though just brushing the beam has not much affect the longer you touch it the beam the hotter it becomes. The beam can be fired in a length determined by the casters natural energy stat and has a strength determined by their willpower.

Meltabeam
(Ethereal creation)
The touched being is encased in an armor of magma fire and stone. Surprisingly the wearer feels no heat at all from this. Everything else however does. Things coming in direct contact with the wearers armor will burn up as if they had touched real magma.
Magma armor
(Bless/Curse)
 

3 Point magma magic.

  
Fissure
(Summon element)
 The only warning is the ground rumbling in this fearsome spell. The caster summons a ball of burning gasses from deep within the planet to crush its way up bringing a tendril of magma with it. When the gas bursts through the ground in a dark flaming cloud it rapidly continues its way up through the sky. Any unlucky enough to be caught in this cloud suffer from intense heat burns. Any unluckier than that hang around for the magma burst that follows it. Like the ground devour this spell can have huge long term consequences.

Magma golem
(Summon Elemental Spirit)
A walking mass of molten stone, the magma golem is perhaps the single most dangerous summoned creature in any of the example trees. It lumbers along starting at the size of a 2 story building. Things that touch it suffer severe burns things that get absorbed into have a worse fate. As it walks its mass slowly depletes as it leaves parts of itself behind. When it becomes too small to move it curls into a ball and explodes like a bubble of fire and stone.
 

4 Point magma magic.

  
This spell is the hastened process that ground devour or fissure begins. It starts like fissure in that it begins with a trembling of the ground a bursting explosion of heated gas followed by A pillar of pressurized magma launching itself from the ground and raining down all over the battlefield. Over time this pillar will seem to die down but by then the battlefield will have changed to a magma flat. Over time this flat will grow into a fully fledged volcano.
Volcano
(Summon element)