Year 1 you spend doing "algebra" and real analysis 1. The algebra professor has been around long enough that she was my professor's professor, and real analysis has a different guy every year. Algebra starts with prepositional logic, the goes into proofs (what a formal proof is and is not, proofs by induction), combinatorics, modulo arithmetic and primes/coprimes, polynomial algebra, matrix algebra, and a bunch of shit I'm likely forgetting. Real analysis 1 basically ends at the two fundamental theorems of calculus. The subjects aren't hard, the immediate demand of rigour and focus on formal proofs is. Both start being 300 person auditoriums and whittle down to maybe 30 or so people.
Year 2 filter is a class which condenses linear algebra, numerical analysis and programming (Fortran is used) into one year-long class. The problem is the breadth of subjects in a single class and, again, the mathematical rigour imposed. You also have real analysis 2 which is the same shit as 1 but multivariate and special math 1 which is analysis on the complex plane.
Year 3 has your ass (mostly) done with pure math classes by now and you're looking at no filter classes and a decently light workload. The DSP and ODE/PDE (special math 2) classes are probably the most challenging.
Year 4 of my major has you doing interior earth physics, gravimetry, geomagnetism and seismology. This is crunch year. IEP is a bitch but doable. The big problem is having to do all of them concurrently.
Year 5 is an applied electronics class and then a bunch of "such-and-so prospecting method" classes. High course load, but no filters.
Throughout all of this you also have a ton more classes, mostly physics classes which are usually a pleasure irregardless of difficulty, and geology classes which are piss easy and mostly an excuse to get drunk and party on field excursions. Also several major specific classes that aren't worth mentioning since they're considered pushover classes, like geodesy.
